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 118 <span class="pre noprint docinfo top">[<a style="" href="http://tools.ietf.org/html/" title="Document search and retrieval page">RFCs/IDs</a>] [<a href="http://tools.ietf.org/rfc/rfc2445.txt" title="Plaintext version of this document">Plain</a>] [From <a href="http://tools.ietf.org/html/draft-ietf-calsch-ical">draft-ietf-calsch-ical</a>]                        </span><br>
 119 <span class="pre noprint docinfo">                                                                        </span><br>
 120 <span class="pre noprint docinfo">                                                       PROPOSED STANDARD</span><br>
 121 <span class="pre noprint docinfo">                                                                  <a style="" href="http://www.rfc-editor.org/errata_search.php?rfc=2445">Errata</a></span><br>
 122 <pre>Network Working Group                                         F. Dawson
 123 Request for Comments: 2445                                        Lotus
 124 Category: Standards Track                                  D. Stenerson
 125                                                               Microsoft
 126                                                           November 1998
 127
 128
 129      <span class="h1"><h1>Internet Calendaring and Scheduling Core Object Specification</h1></span>
 130                               <span class="h1"><h1>(iCalendar)</h1></span>
 131
 132 Status of this Memo
 133
 134    This document specifies an Internet standards track protocol for the
 135    Internet community, and requests discussion and suggestions for
 136    improvements.  Please refer to the current edition of the "Internet
 137    Official Protocol Standards" (STD 1) for the standardization state
 138    and status of this protocol.  Distribution of this memo is unlimited.
 139
 140 Copyright Notice
 141
 142    Copyright (C) The Internet Society (1998).  All Rights Reserved.
 143
 144 Abstract
 145
 146    There is a clear need to provide and deploy interoperable calendaring
 147    and scheduling services for the Internet. Current group scheduling
 148    and Personal Information Management (PIM) products are being extended
 149    for use across the Internet, today, in proprietary ways. This memo
 150    has been defined to provide the definition of a common format for
 151    openly exchanging calendaring and scheduling information across the
 152    Internet.
 153
 154    This memo is formatted as a registration for a MIME media type per
 155    [<a href="http://tools.ietf.org/html/rfc2048" title="&quot;Multipurpose Internet Mail Extensions (MIME) - Part Four: Registration Procedures&quot;">RFC 2048</a>]. However, the format in this memo is equally applicable
 156    for use outside of a MIME message content type.
 157
 158    The proposed media type value is 'text/calendar'. This string would
 159    label a media type containing calendaring and scheduling information
 160    encoded as text characters formatted in a manner outlined below.
 161
 162    This MIME media type provides a standard content type for capturing
 163    calendar event, to-do and journal entry information. It also can be
 164    used to convey free/busy time information. The content type is
 165    suitable as a MIME message entity that can be transferred over MIME
 166    based email systems, using HTTP or some other Internet transport. In
 167
 168
 169
 170
 171
 172
 173 <span class="grey">Dawson &amp; Stenerson          Standards Track                     [Page 1]</span>
 174 </pre><pre class="newpage"><a name="page-2" id="page-2" href="#page-2" class="invisible"> </a>
 175 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 176
 177
 178    addition, the content type is useful as an object for interactions
 179    between desktop applications using the operating system clipboard,
 180    drag/drop or file systems capabilities.
 181
 182    This memo is based on the earlier work of the vCalendar specification
 183    for the exchange of personal calendaring and scheduling information.
 184    In order to avoid confusion with this referenced work, this memo is
 185    to be known as the iCalendar specification.
 186
 187    This memo defines the format for specifying iCalendar object methods.
 188    An iCalendar object method is a set of usage constraints for the
 189    iCalendar object. For example, these methods might define scheduling
 190    messages that request an event be scheduled, reply to an event
 191    request, send a cancellation notice for an event, modify or replace
 192    the definition of an event, provide a counter proposal for an
 193    original event request, delegate an event request to another
 194    individual, request free or busy time, reply to a free or busy time
 195    request, or provide similar scheduling messages for a to-do or
 196    journal entry calendar component. The iCalendar Transport-indendent
 197    Interoperability Protocol (iTIP) defined in [<a href="#ref-ITIP" title="&quot;iCalendar Transport-Independent Interoperability Protocol (iTIP) : Scheduling Events, Busy Time, To-dos and Journal Entries&quot;">ITIP</a>] is one such
 198    scheduling protocol.
 199
 200 Table of Contents
 201
 202    <a href="#section-1">1</a> Introduction.....................................................<a href="#page-5">5</a>
 203    <a href="#section-2">2</a> Basic Grammar and Conventions....................................<a href="#page-6">6</a>
 204     <a href="#section-2.1">2.1</a> Formatting Conventions .......................................<a href="#page-7">7</a>
 205     <a href="#section-2.2">2.2</a> Related Memos ................................................<a href="#page-8">8</a>
 206     <a href="#section-2.3">2.3</a> International Considerations .................................<a href="#page-8">8</a>
 207    <a href="#section-3">3</a> Registration Information.........................................<a href="#page-8">8</a>
 208     <a href="#section-3.1">3.1</a> Content Type .................................................<a href="#page-8">8</a>
 209     <a href="#section-3.2">3.2</a> Parameters ...................................................<a href="#page-9">9</a>
 210     <a href="#section-3.3">3.3</a> Content Header Fields .......................................<a href="#page-10">10</a>
 211     <a href="#section-3.4">3.4</a> Encoding Considerations .....................................<a href="#page-10">10</a>
 212     <a href="#section-3.5">3.5</a> Security Considerations .....................................<a href="#page-10">10</a>
 213     <a href="#section-3.6">3.6</a> Interoperability Considerations .............................<a href="#page-11">11</a>
 214     <a href="#section-3.7">3.7</a> Applications Which Use This Media Type ......................<a href="#page-11">11</a>
 215     <a href="#section-3.8">3.8</a> Additional Information ......................................<a href="#page-11">11</a>
 216     <a href="#section-3.9">3.9</a> Magic Numbers ...............................................<a href="#page-11">11</a>
 217     <a href="#section-3.10">3.10</a> File Extensions ............................................<a href="#page-11">11</a>
 218     <a href="#section-3.11">3.11</a> Contact for Further Information: ...........................<a href="#page-12">12</a>
 219     <a href="#section-3.12">3.12</a> Intended Usage .............................................<a href="#page-12">12</a>
 220     <a href="#section-3.13">3.13</a> Authors/Change Controllers .................................<a href="#page-12">12</a>
 221    <a href="#section-4">4</a> iCalendar Object Specification..................................<a href="#page-13">13</a>
 222     <a href="#section-4.1">4.1</a> Content Lines ...............................................<a href="#page-13">13</a>
 223      <a href="#section-4.1.1">4.1.1</a> List and Field Separators ................................<a href="#page-16">16</a>
 224      <a href="#section-4.1.2">4.1.2</a> Multiple Values ..........................................<a href="#page-16">16</a>
 225      <a href="#section-4.1.3">4.1.3</a> Binary Content ...........................................<a href="#page-16">16</a>
 226
 227
 228
 229 <span class="grey">Dawson &amp; Stenerson          Standards Track                     [Page 2]</span>
 230 </pre><pre class="newpage"><a name="page-3" id="page-3" href="#page-3" class="invisible"> </a>
 231 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 232
 233
 234      <a href="#section-4.1.4">4.1.4</a> Character Set ............................................<a href="#page-17">17</a>
 235     <a href="#section-4.2">4.2</a> Property Parameters .........................................<a href="#page-17">17</a>
 236      <a href="#section-4.2.1">4.2.1</a> Alternate Text Representation ............................<a href="#page-18">18</a>
 237      <a href="#section-4.2.2">4.2.2</a> Common Name ..............................................<a href="#page-19">19</a>
 238      <a href="#section-4.2.3">4.2.3</a> Calendar User Type .......................................<a href="#page-20">20</a>
 239      <a href="#section-4.2.4">4.2.4</a> Delegators ...............................................<a href="#page-20">20</a>
 240      <a href="#section-4.2.5">4.2.5</a> Delegatees ...............................................<a href="#page-21">21</a>
 241      <a href="#section-4.2.6">4.2.6</a> Directory Entry Reference ................................<a href="#page-21">21</a>
 242      <a href="#section-4.2.7">4.2.7</a> Inline Encoding ..........................................<a href="#page-22">22</a>
 243      <a href="#section-4.2.8">4.2.8</a> Format Type ..............................................<a href="#page-23">23</a>
 244      <a href="#section-4.2.9">4.2.9</a> Free/Busy Time Type ......................................<a href="#page-23">23</a>
 245      <a href="#section-4.2.10">4.2.10</a> Language ................................................<a href="#page-24">24</a>
 246      <a href="#section-4.2.11">4.2.11</a> Group or List Membership ................................<a href="#page-25">25</a>
 247      <a href="#section-4.2.12">4.2.12</a> Participation Status ....................................<a href="#page-25">25</a>
 248      <a href="#section-4.2.13">4.2.13</a> Recurrence Identifier Range .............................<a href="#page-27">27</a>
 249      <a href="#section-4.2.14">4.2.14</a> Alarm Trigger Relationship ..............................<a href="#page-27">27</a>
 250      <a href="#section-4.2.15">4.2.15</a> Relationship Type .......................................<a href="#page-28">28</a>
 251      <a href="#section-4.2.16">4.2.16</a> Participation Role ......................................<a href="#page-29">29</a>
 252      <a href="#section-4.2.17">4.2.17</a> RSVP Expectation ........................................<a href="#page-29">29</a>
 253      <a href="#section-4.2.18">4.2.18</a> Sent By .................................................<a href="#page-30">30</a>
 254      <a href="#section-4.2.19">4.2.19</a> Time Zone Identifier ....................................<a href="#page-30">30</a>
 255      <a href="#section-4.2.20">4.2.20</a> Value Data Types ........................................<a href="#page-32">32</a>
 256     <a href="#section-4.3">4.3</a> Property Value Data Types ...................................<a href="#page-32">32</a>
 257      <a href="#section-4.3.1">4.3.1</a> Binary ...................................................<a href="#page-33">33</a>
 258      <a href="#section-4.3.2">4.3.2</a> Boolean ..................................................<a href="#page-33">33</a>
 259      <a href="#section-4.3.3">4.3.3</a> Calendar User Address ....................................<a href="#page-34">34</a>
 260      <a href="#section-4.3.4">4.3.4</a> Date .....................................................<a href="#page-34">34</a>
 261      <a href="#section-4.3.5">4.3.5</a> Date-Time ................................................<a href="#page-35">35</a>
 262      <a href="#section-4.3.6">4.3.6</a> Duration .................................................<a href="#page-37">37</a>
 263      <a href="#section-4.3.7">4.3.7</a> Float ....................................................<a href="#page-38">38</a>
 264      <a href="#section-4.3.8">4.3.8</a> Integer ..................................................<a href="#page-38">38</a>
 265      <a href="#section-4.3.9">4.3.9</a> Period of Time ...........................................<a href="#page-39">39</a>
 266      <a href="#section-4.3.10">4.3.10</a> Recurrence Rule .........................................<a href="#page-40">40</a>
 267      <a href="#section-4.3.11">4.3.11</a> Text ....................................................<a href="#page-45">45</a>
 268      <a href="#section-4.3.12">4.3.12</a> Time ....................................................<a href="#page-47">47</a>
 269      <a href="#section-4.3.13">4.3.13</a> URI .....................................................<a href="#page-49">49</a>
 270      <a href="#section-4.3.14">4.3.14</a> UTC Offset ..............................................<a href="#page-49">49</a>
 271     <a href="#section-4.4">4.4</a> iCalendar Object ............................................<a href="#page-50">50</a>
 272     <a href="#section-4.5">4.5</a> Property ....................................................<a href="#page-51">51</a>
 273     <a href="#section-4.6">4.6</a> Calendar Components .........................................<a href="#page-51">51</a>
 274      <a href="#section-4.6.1">4.6.1</a> Event Component ..........................................<a href="#page-52">52</a>
 275      <a href="#section-4.6.2">4.6.2</a> To-do Component ..........................................<a href="#page-55">55</a>
 276      <a href="#section-4.6.3">4.6.3</a> Journal Component ........................................<a href="#page-56">56</a>
 277      <a href="#section-4.6.4">4.6.4</a> Free/Busy Component ......................................<a href="#page-58">58</a>
 278      <a href="#section-4.6.5">4.6.5</a> Time Zone Component ......................................<a href="#page-60">60</a>
 279      <a href="#section-4.6.6">4.6.6</a> Alarm Component ..........................................<a href="#page-67">67</a>
 280     <a href="#section-4.7">4.7</a> Calendar Properties .........................................<a href="#page-73">73</a>
 281      <a href="#section-4.7.1">4.7.1</a> Calendar Scale ...........................................<a href="#page-73">73</a>
 282
 283
 284
 285 <span class="grey">Dawson &amp; Stenerson          Standards Track                     [Page 3]</span>
 286 </pre><pre class="newpage"><a name="page-4" id="page-4" href="#page-4" class="invisible"> </a>
 287 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 288
 289
 290      <a href="#section-4.7.2">4.7.2</a> Method ...................................................<a href="#page-74">74</a>
 291      <a href="#section-4.7.3">4.7.3</a> Product Identifier .......................................<a href="#page-75">75</a>
 292      <a href="#section-4.7.4">4.7.4</a> Version ..................................................<a href="#page-76">76</a>
 293     <a href="#section-4.8">4.8</a> Component Properties ........................................<a href="#page-77">77</a>
 294      <a href="#section-4.8.1">4.8.1</a> Descriptive Component Properties .........................<a href="#page-77">77</a>
 295        <a href="#section-4.8.1.1">4.8.1.1</a> Attachment ...........................................<a href="#page-77">77</a>
 296        <a href="#section-4.8.1.2">4.8.1.2</a> Categories ...........................................<a href="#page-78">78</a>
 297        <a href="#section-4.8.1.3">4.8.1.3</a> Classification .......................................<a href="#page-79">79</a>
 298        <a href="#section-4.8.1.4">4.8.1.4</a> Comment ..............................................<a href="#page-80">80</a>
 299        <a href="#section-4.8.1.5">4.8.1.5</a> Description ..........................................<a href="#page-81">81</a>
 300        <a href="#section-4.8.1.6">4.8.1.6</a> Geographic Position ..................................<a href="#page-82">82</a>
 301        <a href="#section-4.8.1.7">4.8.1.7</a> Location .............................................<a href="#page-84">84</a>
 302        <a href="#section-4.8.1.8">4.8.1.8</a> Percent Complete .....................................<a href="#page-85">85</a>
 303        <a href="#section-4.8.1.9">4.8.1.9</a> Priority .............................................<a href="#page-85">85</a>
 304        <a href="#section-4.8.1.10">4.8.1.10</a> Resources ...........................................<a href="#page-87">87</a>
 305        <a href="#section-4.8.1.11">4.8.1.11</a> Status ..............................................<a href="#page-88">88</a>
 306        <a href="#section-4.8.1.12">4.8.1.12</a> Summary .............................................<a href="#page-89">89</a>
 307      <a href="#section-4.8.2">4.8.2</a> Date and Time Component Properties .......................<a href="#page-90">90</a>
 308        <a href="#section-4.8.2.1">4.8.2.1</a> Date/Time Completed ..................................<a href="#page-90">90</a>
 309        <a href="#section-4.8.2.2">4.8.2.2</a> Date/Time End ........................................<a href="#page-91">91</a>
 310        <a href="#section-4.8.2.3">4.8.2.3</a> Date/Time Due ........................................<a href="#page-92">92</a>
 311        <a href="#section-4.8.2.4">4.8.2.4</a> Date/Time Start ......................................<a href="#page-93">93</a>
 312        <a href="#section-4.8.2.5">4.8.2.5</a> Duration .............................................<a href="#page-94">94</a>
 313        <a href="#section-4.8.2.6">4.8.2.6</a> Free/Busy Time .......................................<a href="#page-95">95</a>
 314        <a href="#section-4.8.2.7">4.8.2.7</a> Time Transparency ....................................<a href="#page-96">96</a>
 315      <a href="#section-4.8.3">4.8.3</a> Time Zone Component Properties ...........................<a href="#page-97">97</a>
 316        <a href="#section-4.8.3.1">4.8.3.1</a> Time Zone Identifier .................................<a href="#page-97">97</a>
 317        <a href="#section-4.8.3.2">4.8.3.2</a> Time Zone Name .......................................<a href="#page-98">98</a>
 318        <a href="#section-4.8.3.3">4.8.3.3</a> Time Zone Offset From ................................<a href="#page-99">99</a>
 319        <a href="#section-4.8.3.4">4.8.3.4</a> Time Zone Offset To .................................<a href="#page-100">100</a>
 320        <a href="#section-4.8.3.5">4.8.3.5</a> Time Zone URL .......................................<a href="#page-101">101</a>
 321      <a href="#section-4.8.4">4.8.4</a> Relationship Component Properties .......................<a href="#page-102">102</a>
 322        <a href="#section-4.8.4.1">4.8.4.1</a> Attendee ............................................<a href="#page-102">102</a>
 323        <a href="#section-4.8.4.2">4.8.4.2</a> Contact .............................................<a href="#page-104">104</a>
 324        <a href="#section-4.8.4.3">4.8.4.3</a> Organizer ...........................................<a href="#page-106">106</a>
 325        <a href="#section-4.8.4.4">4.8.4.4</a> Recurrence ID .......................................<a href="#page-107">107</a>
 326        <a href="#section-4.8.4.5">4.8.4.5</a> Related To ..........................................<a href="#page-109">109</a>
 327        <a href="#section-4.8.4.6">4.8.4.6</a> Uniform Resource Locator ............................<a href="#page-110">110</a>
 328        <a href="#section-4.8.4.7">4.8.4.7</a> Unique Identifier ...................................<a href="#page-111">111</a>
 329      <a href="#section-4.8.5">4.8.5</a> Recurrence Component Properties .........................<a href="#page-112">112</a>
 330        <a href="#section-4.8.5.1">4.8.5.1</a> Exception Date/Times ................................<a href="#page-112">112</a>
 331        <a href="#section-4.8.5.2">4.8.5.2</a> Exception Rule ......................................<a href="#page-114">114</a>
 332        <a href="#section-4.8.5.3">4.8.5.3</a> Recurrence Date/Times ...............................<a href="#page-115">115</a>
 333        <a href="#section-4.8.5.4">4.8.5.4</a> Recurrence Rule .....................................<a href="#page-117">117</a>
 334      <a href="#section-4.8.6">4.8.6</a> Alarm Component Properties ..............................<a href="#page-126">126</a>
 335        <a href="#section-4.8.6.1">4.8.6.1</a> Action ..............................................<a href="#page-126">126</a>
 336        <a href="#section-4.8.6.2">4.8.6.2</a> Repeat Count ........................................<a href="#page-126">126</a>
 337        <a href="#section-4.8.6.3">4.8.6.3</a> Trigger .............................................<a href="#page-127">127</a>
 338
 339
 340
 341 <span class="grey">Dawson &amp; Stenerson          Standards Track                     [Page 4]</span>
 342 </pre><pre class="newpage"><a name="page-5" id="page-5" href="#page-5" class="invisible"> </a>
 343 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 344
 345
 346      <a href="#section-4.8.7">4.8.7</a> Change Management Component Properties ..................<a href="#page-129">129</a>
 347        <a href="#section-4.8.7.1">4.8.7.1</a> Date/Time Created ...................................<a href="#page-129">129</a>
 348        <a href="#section-4.8.7.2">4.8.7.2</a> Date/Time Stamp .....................................<a href="#page-130">130</a>
 349        <a href="#section-4.8.7.3">4.8.7.3</a> Last Modified .......................................<a href="#page-131">131</a>
 350        <a href="#section-4.8.7.4">4.8.7.4</a> Sequence Number .....................................<a href="#page-131">131</a>
 351      <a href="#section-4.8.8">4.8.8</a> Miscellaneous Component Properties ......................<a href="#page-133">133</a>
 352        <a href="#section-4.8.8.1">4.8.8.1</a> Non-standard Properties .............................<a href="#page-133">133</a>
 353        <a href="#section-4.8.8.2">4.8.8.2</a> Request Status ......................................<a href="#page-134">134</a>
 354    <a href="#section-5">5</a> iCalendar Object Examples......................................<a href="#page-136">136</a>
 355    <a href="#section-6">6</a> Recommended Practices..........................................<a href="#page-140">140</a>
 356    <a href="#section-7">7</a> Registration of Content Type Elements..........................<a href="#page-141">141</a>
 357     <a href="#section-7.1">7.1</a> Registration of New and Modified iCalendar Object Methods ..<a href="#page-141">141</a>
 358     <a href="#section-7.2">7.2</a> Registration of New Properties .............................<a href="#page-141">141</a>
 359      <a href="#section-7.2.1">7.2.1</a> Define the property .....................................<a href="#page-142">142</a>
 360      <a href="#section-7.2.2">7.2.2</a> Post the Property definition ............................<a href="#page-143">143</a>
 361      <a href="#section-7.2.3">7.2.3</a> Allow a comment period ..................................<a href="#page-143">143</a>
 362      <a href="#section-7.2.4">7.2.4</a> Submit the property for approval ........................<a href="#page-143">143</a>
 363     <a href="#section-7.3">7.3</a> Property Change Control ....................................<a href="#page-143">143</a>
 364    <a href="#section-8">8</a> References.....................................................<a href="#page-144">144</a>
 365    <a href="#section-9">9</a> Acknowledgments................................................<a href="#page-145">145</a>
 366    <a href="#section-10">10</a> Authors' and Chairs' Addresses................................<a href="#page-146">146</a>
 367    <a href="#section-11">11</a> Full Copyright Statement......................................<a href="#page-148">148</a>
 368
 369 <span class="h2"><h2><a name="section-1">1</a> Introduction</h2></span>
 370
 371    The use of calendaring and scheduling has grown considerably in the
 372    last decade. Enterprise and inter-enterprise business has become
 373    dependent on rapid scheduling of events and actions using this
 374    information technology. However, the longer term growth of
 375    calendaring and scheduling, is currently limited by the lack of
 376    Internet standards for the message content types that are central to
 377    these knowledgeware applications. This memo is intended to progress
 378    the level of interoperability possible between dissimilar calendaring
 379    and scheduling applications. This memo defines a MIME content type
 380    for exchanging electronic calendaring and scheduling information. The
 381    Internet Calendaring and Scheduling Core Object Specification, or
 382    iCalendar, allows for the capture and exchange of information
 383    normally stored within a calendaring and scheduling application; such
 384    as a Personal Information Manager (PIM) or a Group Scheduling
 385    product.
 386
 387    The iCalendar format is suitable as an exchange format between
 388    applications or systems. The format is defined in terms of a MIME
 389    content type. This will enable the object to be exchanged using
 390    several transports, including but not limited to SMTP, HTTP, a file
 391    system, desktop interactive protocols such as the use of a memory-
 392    based clipboard or drag/drop interactions, point-to-point
 393    asynchronous communication, wired-network transport, or some form of
 394
 395
 396
 397 <span class="grey">Dawson &amp; Stenerson          Standards Track                     [Page 5]</span>
 398 </pre><pre class="newpage"><a name="page-6" id="page-6" href="#page-6" class="invisible"> </a>
 399 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 400
 401
 402    unwired transport such as infrared might also be used.
 403
 404    The memo also provides for the definition of iCalendar object methods
 405    that will map this content type to a set of messages for supporting
 406    calendaring and scheduling operations such as requesting, replying
 407    to, modifying, and canceling meetings or appointments, to-dos and
 408    journal entries. The iCalendar object methods can be used to define
 409    other calendaring and scheduling operations such a requesting for and
 410    replying with free/busy time data. Such a scheduling protocol is
 411    defined in the iCalendar Transport-independent Interoperability
 412    Protocol (iTIP) defined in [<a href="#ref-ITIP" title="&quot;iCalendar Transport-Independent Interoperability Protocol (iTIP) : Scheduling Events, Busy Time, To-dos and Journal Entries&quot;">ITIP</a>].
 413
 414    The memo also includes a formal grammar for the content type based on
 415    the Internet ABNF defined in [<a href="http://tools.ietf.org/html/rfc2234" title="&quot;Augmented BNF for Syntax Specifications: ABNF&quot;">RFC 2234</a>]. This ABNF is required for
 416    the implementation of parsers and to serve as the definitive
 417    reference when ambiguities or questions arise in interpreting the
 418    descriptive prose definition of the memo.
 419
 420 <span class="h2"><h2><a name="section-2">2</a> Basic Grammar and Conventions</h2></span>
 421
 422    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 423    "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY" and
 424    "OPTIONAL" in this document are to be interoperated as described in
 425    [<a href="http://tools.ietf.org/html/rfc2119" title="&quot;Key words for use in RFCs to Indicate Requirement Levels&quot;">RFC 2119</a>].
 426
 427    This memo makes use of both a descriptive prose and a more formal
 428    notation for defining the calendaring and scheduling format.
 429
 430    The notation used in this memo is the ABNF notation of [<a href="http://tools.ietf.org/html/rfc2234" title="&quot;Augmented BNF for Syntax Specifications: ABNF&quot;">RFC 2234</a>].
 431    Readers intending on implementing this format defined in this memo
 432    should be familiar with this notation in order to properly interpret
 433    the specifications of this memo.
 434
 435    All numeric and hexadecimal values used in this memo are given in
 436    decimal notation.
 437
 438    All names of properties, property parameters, enumerated property
 439    values and property parameter values are case-insensitive. However,
 440    all other property values are case-sensitive, unless otherwise
 441    stated.
 442
 443         Note: All indented editorial notes, such as this one, are
 444         intended to provide the reader with additional information. The
 445         information is not essential to the building of an
 446         implementation conformant with this memo. The information is
 447         provided to highlight a particular feature or characteristic of
 448         the memo.
 449
 450
 451
 452
 453 <span class="grey">Dawson &amp; Stenerson          Standards Track                     [Page 6]</span>
 454 </pre><pre class="newpage"><a name="page-7" id="page-7" href="#page-7" class="invisible"> </a>
 455 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 456
 457
 458    The format for the iCalendar object is based on the syntax of the
 459    [<a href="http://tools.ietf.org/html/rfc2425" title="&quot;A MIME Content-Type for Directory Information&quot;">RFC 2425</a>] content type. While the iCalendar object is not a profile
 460    of the [<a href="http://tools.ietf.org/html/rfc2425" title="&quot;A MIME Content-Type for Directory Information&quot;">RFC 2425</a>] content type, it does reuse a number of the
 461    elements from the [<a href="http://tools.ietf.org/html/rfc2425" title="&quot;A MIME Content-Type for Directory Information&quot;">RFC 2425</a>] specification.
 462
 463 <span class="h3"><h3><a name="section-2.1">2.1</a> Formatting Conventions</h3></span>
 464
 465    The mechanisms defined in this memo are defined in prose. Many of the
 466    terms used to describe these have common usage that is different than
 467    the standards usage of this memo. In order to reference within this
 468    memo elements of the calendaring and scheduling model, core object
 469    (this memo) or interoperability protocol [<a href="#ref-ITIP" title="&quot;iCalendar Transport-Independent Interoperability Protocol (iTIP) : Scheduling Events, Busy Time, To-dos and Journal Entries&quot;">ITIP</a>] some formatting
 470    conventions have been used. Calendaring and scheduling roles are
 471    referred to in quoted-strings of text with the first character of
 472    each word in upper case. For example, "Organizer" refers to a role of
 473    a "Calendar User" within the scheduling protocol defined by [<a href="#ref-ITIP" title="&quot;iCalendar Transport-Independent Interoperability Protocol (iTIP) : Scheduling Events, Busy Time, To-dos and Journal Entries&quot;">ITIP</a>].
 474    Calendar components defined by this memo are referred to with
 475    capitalized, quoted-strings of text. All calendar components start
 476    with the letter "V". For example, "VEVENT" refers to the event
 477    calendar component, "VTODO" refers to the to-do calendar component
 478    and "VJOURNAL" refers to the daily journal calendar component.
 479    Scheduling methods defined by [<a href="#ref-ITIP" title="&quot;iCalendar Transport-Independent Interoperability Protocol (iTIP) : Scheduling Events, Busy Time, To-dos and Journal Entries&quot;">ITIP</a>] are referred to with
 480    capitalized, quoted-strings of text. For example, "REQUEST" refers to
 481    the method for requesting a scheduling calendar component be created
 482    or modified, "REPLY" refers to the method a recipient of a request
 483    uses to update their status with the "Organizer" of the calendar
 484    component.
 485
 486    The properties defined by this memo are referred to with capitalized,
 487    quoted-strings of text, followed by the word "property". For example,
 488    "ATTENDEE" property refers to the iCalendar property used to convey
 489    the calendar address of a calendar user. Property parameters defined
 490    by this memo are referred to with lowercase, quoted-strings of text,
 491    followed by the word "parameter". For example, "value" parameter
 492    refers to the iCalendar property parameter used to override the
 493    default data type for a property value. Enumerated values defined by
 494    this memo are referred to with capitalized text, either alone or
 495    followed by the word "value". For example, the "MINUTELY" value can
 496    be used with the "FREQ" component of the "RECUR" data type to specify
 497    repeating components based on an interval of one minute or more.
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509 <span class="grey">Dawson &amp; Stenerson          Standards Track                     [Page 7]</span>
 510 </pre><pre class="newpage"><a name="page-8" id="page-8" href="#page-8" class="invisible"> </a>
 511 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 512
 513
 514 <span class="h3"><h3><a name="section-2.2">2.2</a> Related Memos</h3></span>
 515
 516    Implementers will need to be familiar with several other memos that,
 517    along with this memo, form a framework for Internet calendaring and
 518    scheduling standards. This memo, [<a href="#ref-ICAL">ICAL</a>], specifies a core
 519    specification of objects, data types, properties and property
 520    parameters.
 521
 522    [<a name="ref-ITIP" id="ref-ITIP">ITIP</a>] - specifies an interoperability protocol for scheduling
 523    between different implementations;
 524
 525    [<a name="ref-IMIP" id="ref-IMIP">IMIP</a>] specifies an Internet email binding for [<a href="#ref-ITIP" title="&quot;iCalendar Transport-Independent Interoperability Protocol (iTIP) : Scheduling Events, Busy Time, To-dos and Journal Entries&quot;">ITIP</a>].
 526
 527    This memo does not attempt to repeat the specification of concepts or
 528    definitions from these other memos. Where possible, references are
 529    made to the memo that provides for the specification of these
 530    concepts or definitions.
 531
 532 <span class="h3"><h3><a name="section-2.3">2.3</a> International Considerations</h3></span>
 533
 534    In the rest of this document, descriptions of characters are of the
 535    form "character name (codepoint)", where "codepoint" is from the US-
 536    ASCII character set. The "character name" is the authoritative
 537    description; (codepoint) is a reference to that character in US-ASCII
 538    or US-ASCII compatible sets (for example the ISO-8859-x family, UTF-
 539    8, ISO-2022-xx, KOI8-R). If a non-US-ASCII compatible character set
 540    is used, appropriate code-point from that character set MUST be
 541    chosen instead. Use of non-US-ASCII-compatible character sets is NOT
 542    recommended.
 543
 544 <span class="h2"><h2><a name="section-3">3</a>  Registration Information</h2></span>
 545
 546    The Calendaring and Scheduling Core Object Specification is intended
 547    for use as a MIME content type. However, the implementation of the
 548    memo is in no way limited solely as a MIME content type.
 549
 550 <span class="h3"><h3><a name="section-3.1">3.1</a> Content Type</h3></span>
 551
 552    The following text is intended to register this memo as the MIME
 553    content type "text/calendar".
 554
 555      To: ietf-types@uninett.no
 556
 557      Subject: Registration of MIME content type text/calendar.
 558
 559      MIME media type name: text
 560
 561      MIME subtype name: calendar
 562
 563
 564
 565 <span class="grey">Dawson &amp; Stenerson          Standards Track                     [Page 8]</span>
 566 </pre><pre class="newpage"><a name="page-9" id="page-9" href="#page-9" class="invisible"> </a>
 567 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 568
 569
 570 <span class="h3"><h3><a name="section-3.2">3.2</a> Parameters</h3></span>
 571
 572    Required parameters: none
 573
 574    Optional parameters: charset, method, component and optinfo
 575
 576    The "charset" parameter is defined in [<a href="http://tools.ietf.org/html/rfc2046" title="&quot; Multipurpose Internet Mail Extensions (MIME) - Part Two: Media Types&quot;">RFC 2046</a>] for other body
 577    parts. It is used to identify the default character set used within
 578    the body part.
 579
 580    The "method" parameter is used to convey the iCalendar object method
 581    or transaction semantics for the calendaring and scheduling
 582    information. It also is an identifier for the restricted set of
 583    properties and values that the iCalendar object consists of. The
 584    parameter is to be used as a guide for applications interpreting the
 585    information contained within the body part. It SHOULD NOT be used to
 586    exclude or require particular pieces of information unless the
 587    identified method definition specifically calls for this behavior.
 588    Unless specifically forbidden by a particular method definition, a
 589    text/calendar content type can contain any set of properties
 590    permitted by the Calendaring and Scheduling Core Object
 591    Specification. The "method" parameter MUST be the same value as that
 592    specified in the "METHOD" component property in the iCalendar object.
 593    If one is present, the other MUST also be present.
 594
 595    The value for the "method" parameter is defined as follows:
 596
 597         method  = 1*(ALPHA / DIGIT / "-")
 598         ; IANA registered iCalendar object method
 599
 600    The "component" parameter conveys the type of iCalendar calendar
 601    component within the body part. If the iCalendar object contains more
 602    than one calendar component type, then multiple component parameters
 603    MUST be specified.
 604
 605    The value for the "component" parameter is defined as follows:
 606
 607         component       = ("VEVENT" / "VTODO" / "VJOURNAL" / "VFREEBUSY"
 608                         / "VTIMEZONE" / x-name / iana-token)
 609
 610    The "optinfo" parameter conveys optional information about the
 611    iCalendar object within the body part. This parameter can only
 612    specify semantics already specified by the iCalendar object and that
 613    can be otherwise determined by parsing the body part. In addition,
 614    the optional information specified by this parameter MUST be
 615    consistent with that information specified by the iCalendar object.
 616    For example, it can be used to convey the "Attendee" response status
 617    to a meeting request. The parameter value consists of a string value.
 618
 619
 620
 621 <span class="grey">Dawson &amp; Stenerson          Standards Track                     [Page 9]</span>
 622 </pre><pre class="newpage"><a name="page-10" id="page-10" href="#page-10" class="invisible"> </a>
 623 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 624
 625
 626    The parameter can be specified multiple times.
 627
 628    This parameter MAY only specify semantics already specified by the
 629    iCalendar object and that can be otherwise determined by parsing the
 630    body part.
 631
 632    The value for the "optinfo" parameter is defined as follows:
 633
 634         optinfo = infovalue / qinfovalue
 635
 636         infovalue       = iana-token / x-name
 637
 638         qinfovalue      = DQUOTE (infovalue) DQUOTE
 639
 640 <span class="h3"><h3><a name="section-3.3">3.3</a> Content Header Fields</h3></span>
 641
 642    Optional content header fields: Any header fields defined by [RFC
 643    2045].
 644
 645 <span class="h3"><h3><a name="section-3.4">3.4</a> Encoding Considerations</h3></span>
 646
 647    This MIME content type can contain 8bit characters, so the use of
 648    quoted-printable or BASE64 MIME content-transfer-encodings might be
 649    necessary when iCalendar objects are transferred across protocols
 650    restricted to the 7bit repertoire. Note that a text valued property
 651    in the content entity can also have content encoding of special
 652    characters using a BACKSLASH character (US-ASCII decimal 92)
 653    escapement technique. This means that content values can end up
 654    encoded twice.
 655
 656 <span class="h3"><h3><a name="section-3.5">3.5</a> Security Considerations</h3></span>
 657
 658    SPOOFING - - In this memo, the "Organizer" is the only person
 659    authorized to make changes to an existing "VEVENT", "VTODO",
 660    "VJOURNAL" calendar component and redistribute the updates to the
 661    "Attendees". An iCalendar object that maliciously changes or cancels
 662    an existing "VEVENT", "VTODO" or "VJOURNAL" or "VFREEBUSY" calendar
 663    component might be constructed by someone other than the "Organizer"
 664    and sent to the "Attendees". In addition in this memo, other than the
 665    "Organizer", an "Attendee" of a "VEVENT", "VTODO", "VJOURNAL"
 666    calendar component is the only other person authorized to update any
 667    parameter associated with their "ATTENDEE" property and send it to
 668    the "Organizer". An iCalendar object that maliciously changes the
 669    "ATTENDEE" parameters can be constructed by someone other than the
 670    real "Attendee" and sent to the "Organizer".
 671
 672
 673
 674
 675
 676
 677 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 10]</span>
 678 </pre><pre class="newpage"><a name="page-11" id="page-11" href="#page-11" class="invisible"> </a>
 679 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 680
 681
 682    PROCEDURAL ALARMS - - An iCalendar object can be created that
 683    contains a "VEVENT" and "VTODO" calendar component with "VALARM"
 684    calendar components. The "VALARM" calendar component can be of type
 685    PROCEDURE and can have an attachment containing some sort of
 686    executable program. Implementations that incorporate these types of
 687    alarms are subject to any virus or malicious attack that might occur
 688    as a result of executing the attachment.
 689
 690    ATTACHMENTS - - An iCalendar object can include references to Uniform
 691    Resource Locators that can be programmed resources.
 692
 693    Implementers and users of this memo should be aware of the network
 694    security implications of accepting and parsing such information. In
 695    addition, the security considerations observed by implementations of
 696    electronic mail systems should be followed for this memo.
 697
 698 <span class="h3"><h3><a name="section-3.6">3.6</a> Interoperability Considerations</h3></span>
 699
 700    This MIME content type is intended to define a common format for
 701    conveying calendaring and scheduling information between different
 702    systems. It is heavily based on the earlier [<a href="#ref-VCAL" title="&quot;vCalendar - The Electronic Calendaring and Scheduling Exchange Format&quot;">VCAL</a>] industry
 703    specification.
 704
 705 <span class="h3"><h3><a name="section-3.7">3.7</a> Applications Which Use This Media Type</h3></span>
 706
 707    This content-type is designed for widespread use by Internet
 708    calendaring and scheduling applications. In addition, applications in
 709    the workflow and document management area might find this content-
 710    type applicable. The [<a href="#ref-ITIP" title="&quot;iCalendar Transport-Independent Interoperability Protocol (iTIP) : Scheduling Events, Busy Time, To-dos and Journal Entries&quot;">ITIP</a>] and [<a href="#ref-IMIP" title="&quot;iCalendar Message-based Interoperability Protocol (IMIP)&quot;">IMIP</a>] Internet protocols directly
 711    use this content-type also. Future work on an Internet calendar
 712    access protocol will utilize this content-type too.
 713
 714 <span class="h3"><h3><a name="section-3.8">3.8</a> Additional Information</h3></span>
 715
 716    This memo defines this content-type.
 717
 718 <span class="h3"><h3><a name="section-3.9">3.9</a> Magic Numbers</h3></span>
 719
 720    None.
 721
 722 <span class="h3"><h3><a name="section-3.10">3.10</a> File Extensions</h3></span>
 723
 724    The file extension of "ics" is to be used to designate a file
 725    containing (an arbitrary set of) calendaring and scheduling
 726    information consistent with this MIME content type.
 727
 728
 729
 730
 731
 732
 733 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 11]</span>
 734 </pre><pre class="newpage"><a name="page-12" id="page-12" href="#page-12" class="invisible"> </a>
 735 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 736
 737
 738    The file extension of "ifb" is to be used to designate a file
 739    containing free or busy time information consistent with this MIME
 740    content type.
 741
 742    Macintosh file type codes: The file type code of "iCal" is to be used
 743    in Apple MacIntosh operating system environments to designate a file
 744    containing calendaring and scheduling information consistent with
 745    this MIME media type.
 746
 747    The file type code of "iFBf" is to be used in Apple MacIntosh
 748    operating system environments to designate a file containing free or
 749    busy time information consistent with this MIME media type.
 750
 751 <span class="h3"><h3><a name="section-3.11">3.11</a> Contact for Further Information:</h3></span>
 752
 753    Frank Dawson
 754    6544 Battleford Drive
 755    Raleigh, NC 27613-3502
 756    919-676-9515 (Telephone)
 757    919-676-9564 (Data/Facsimile)
 758    Frank_Dawson@Lotus.com (Internet Mail)
 759
 760    Derik Stenerson
 761    One Microsoft Way
 762    Redmond, WA  98052-6399
 763    425-936-5522 (Telephone)
 764    425-936-7329 (Facsimile)
 765    deriks@microsoft.com (Internet Mail)
 766
 767 <span class="h3"><h3><a name="section-3.12">3.12</a> Intended Usage</h3></span>
 768
 769    COMMON
 770
 771 <span class="h3"><h3><a name="section-3.13">3.13</a> Authors/Change Controllers</h3></span>
 772
 773    Frank Dawson
 774    6544 Battleford Drive
 775    Raleigh, NC 27613-3502
 776    919-676-9515 (Telephone)
 777    919-676-9564 (Data/Facsimile)
 778    Frank_Dawson@Lotus.com (Internet Mail)
 779
 780    Derik Stenerson
 781    One Microsoft Way
 782    Redmond, WA  98052-6399
 783    425-936-5522 (Telephone)
 784    425-936-7329 (Facsimile)
 785    deriks@microsoft.com (Internet Mail)
 786
 787
 788
 789 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 12]</span>
 790 </pre><pre class="newpage"><a name="page-13" id="page-13" href="#page-13" class="invisible"> </a>
 791 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 792
 793
 794 <span class="h2"><h2><a name="section-4">4</a> iCalendar Object Specification</h2></span>
 795
 796    The following sections define the details of a Calendaring and
 797    Scheduling Core Object Specification. This information is intended to
 798    be an integral part of the MIME content type registration. In
 799    addition, this information can be used independent of such content
 800    registration. In particular, this memo has direct applicability for
 801    use as a calendaring and scheduling exchange format in file-, memory-
 802    or network-based transport mechanisms.
 803
 804 <span class="h3"><h3><a name="section-4.1">4.1</a> Content Lines</h3></span>
 805
 806    The iCalendar object is organized into individual lines of text,
 807    called content lines. Content lines are delimited by a line break,
 808    which is a CRLF sequence (US-ASCII decimal 13, followed by US-ASCII
 809    decimal 10).
 810
 811    Lines of text SHOULD NOT be longer than 75 octets, excluding the line
 812    break. Long content lines SHOULD be split into a multiple line
 813    representations using a line "folding" technique. That is, a long
 814    line can be split between any two characters by inserting a CRLF
 815    immediately followed by a single linear white space character (i.e.,
 816    SPACE, US-ASCII decimal 32 or HTAB, US-ASCII decimal 9). Any sequence
 817    of CRLF followed immediately by a single linear white space character
 818    is ignored (i.e., removed) when processing the content type.
 819
 820    For example the line:
 821
 822      DESCRIPTION:This is a long description that exists on a long line.
 823
 824    Can be represented as:
 825
 826      DESCRIPTION:This is a lo
 827       ng description
 828        that exists on a long line.
 829
 830    The process of moving from this folded multiple line representation
 831    to its single line representation is called "unfolding". Unfolding is
 832    accomplished by removing the CRLF character and the linear white
 833    space character that immediately follows.
 834
 835    When parsing a content line, folded lines MUST first be unfolded
 836    according to the unfolding procedure described above. When generating
 837    a content line, lines longer than 75 octets SHOULD be folded
 838    according to the folding procedure described above.
 839
 840
 841
 842
 843
 844
 845 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 13]</span>
 846 </pre><pre class="newpage"><a name="page-14" id="page-14" href="#page-14" class="invisible"> </a>
 847 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 848
 849
 850    The content information associated with an iCalendar object is
 851    formatted using a syntax similar to that defined by [<a href="http://tools.ietf.org/html/rfc2425" title="&quot;A MIME Content-Type for Directory Information&quot;">RFC 2425</a>]. That
 852    is, the content information consists of CRLF-separated content lines.
 853
 854    The following notation defines the lines of content in an iCalendar
 855    object:
 856
 857      contentline        = name *(";" param ) ":" value CRLF
 858         ; This ABNF is just a general definition for an initial parsing
 859         ; of the content line into its property name, parameter list,
 860         ; and value string
 861
 862      ; When parsing a content line, folded lines MUST first
 863         ; be unfolded according to the unfolding procedure
 864         ; described above. When generating a content line, lines
 865         ; longer than 75 octets SHOULD be folded according to
 866         ; the folding procedure described above.
 867
 868      name               = x-name / iana-token
 869
 870      iana-token = 1*(ALPHA / DIGIT / "-")
 871      ; iCalendar identifier registered with IANA
 872
 873      x-name             = "X-" [vendorid "-"] 1*(ALPHA / DIGIT / "-")
 874      ; Reservered for experimental use. Not intended for use in
 875      ; released products.
 876
 877      vendorid   = 3*(ALPHA / DIGIT)     ;Vendor identification
 878
 879      param              = param-name "=" param-value
 880                           *("," param-value)
 881         ; Each property defines the specific ABNF for the parameters
 882         ; allowed on the property. Refer to specific properties for
 883         ; precise parameter ABNF.
 884
 885      param-name = iana-token / x-token
 886
 887      param-value        = paramtext / quoted-string
 888
 889      paramtext  = *SAFE-CHAR
 890
 891      value      = *VALUE-CHAR
 892
 893      quoted-string      = DQUOTE *QSAFE-CHAR DQUOTE
 894
 895      NON-US-ASCII       = %x80-F8
 896      ; Use restricted by charset parameter
 897      ; on outer MIME object (UTF-8 preferred)
 898
 899
 900
 901 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 14]</span>
 902 </pre><pre class="newpage"><a name="page-15" id="page-15" href="#page-15" class="invisible"> </a>
 903 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 904
 905
 906      QSAFE-CHAR = WSP / %x21 / %x23-7E / NON-US-ASCII
 907      ; Any character except CTLs and DQUOTE
 908
 909      SAFE-CHAR  = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-7E
 910                 / NON-US-ASCII
 911      ; Any character except CTLs, DQUOTE, ";", ":", ","
 912
 913      VALUE-CHAR = WSP / %x21-7E / NON-US-ASCII
 914      ; Any textual character
 915
 916      CR = %x0D
 917      ; carriage return
 918
 919      LF = %x0A
 920      ; line feed
 921
 922      CRLF       = CR LF
 923      ; Internet standard newline
 924
 925      CTL        = %x00-08 / %x0A-1F / %x7F
 926         ; Controls
 927
 928      ALPHA      = %x41-5A / %x61-7A   ; A-Z / a-z
 929
 930      DIGIT      = %x30-39
 931         ; 0-9
 932
 933      DQUOTE     = %x22
 934         ; Quotation Mark
 935
 936      WSP        = SPACE / HTAB
 937
 938      SPACE      = %x20
 939
 940      HTAB       = %x09
 941
 942    The property value component of a content line has a format that is
 943    property specific. Refer to the section describing each property for
 944    a definition of this format.
 945
 946    All names of properties, property parameters, enumerated property
 947    values and property parameter values are case-insensitive. However,
 948    all other property values are case-sensitive, unless otherwise
 949    stated.
 950
 951
 952
 953
 954
 955
 956
 957 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 15]</span>
 958 </pre><pre class="newpage"><a name="page-16" id="page-16" href="#page-16" class="invisible"> </a>
 959 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
 960
 961
 962 <span class="h4"><h4><a name="section-4.1.1">4.1.1</a> List and Field Separators</h4></span>
 963
 964    Some properties and parameters allow a list of values. Values in a
 965    list of values MUST be separated by a COMMA character (US-ASCII
 966    decimal 44). There is no significance to the order of values in a
 967    list. For those parameter values (such as those that specify URI
 968    values) that are specified in quoted-strings, the individual quoted-
 969    strings are separated by a COMMA character (US-ASCII decimal 44).
 970
 971    Some property values are defined in terms of multiple parts. These
 972    structured property values MUST have their value parts separated by a
 973    SEMICOLON character (US-ASCII decimal 59).
 974
 975    Some properties allow a list of parameters. Each property parameter
 976    in a list of property parameters MUST be separated by a SEMICOLON
 977    character (US-ASCII decimal 59).
 978
 979    Property parameters with values containing a COLON, a SEMICOLON or a
 980    COMMA character MUST be placed in quoted text.
 981
 982    For example, in the following properties a SEMICOLON is used to
 983    separate property parameters from each other, and a COMMA is used to
 984    separate property values in a value list.
 985
 986      ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT:MAILTO:
 987       jsmith@host.com
 988
 989      RDATE;VALUE=DATE:19970304,19970504,19970704,19970904
 990
 991 <span class="h4"><h4><a name="section-4.1.2">4.1.2</a> Multiple Values</h4></span>
 992
 993    Some properties defined in the iCalendar object can have multiple
 994    values. The general rule for encoding multi-valued items is to simply
 995    create a new content line for each value, including the property
 996    name. However, it should be noted that some properties support
 997    encoding multiple values in a single property by separating the
 998    values with a COMMA character (US-ASCII decimal 44). Individual
 999    property definitions should be consulted for determining whether a
1000    specific property allows multiple values and in which of these two
1001    forms.
1002
1003 <span class="h4"><h4><a name="section-4.1.3">4.1.3</a> Binary Content</h4></span>
1004
1005    Binary content information in an iCalendar object SHOULD be
1006    referenced using a URI within a property value. That is the binary
1007    content information SHOULD be placed in an external MIME entity that
1008    can be referenced by a URI from within the iCalendar object. In
1009    applications where this is not feasible, binary content information
1010
1011
1012
1013 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 16]</span>
1014 </pre><pre class="newpage"><a name="page-17" id="page-17" href="#page-17" class="invisible"> </a>
1015 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1016
1017
1018    can be included within an iCalendar object, but only after first
1019    encoding it into text using the "BASE64" encoding method defined in
1020    [<a href="http://tools.ietf.org/html/rfc2045" title="&quot; Multipurpose Internet Mail Extensions (MIME) - Part One: Format of Internet Message Bodies&quot;">RFC 2045</a>]. Inline binary contact SHOULD only be used in applications
1021    whose special circumstances demand that an iCalendar object be
1022    expressed as a single entity. A property containing inline binary
1023    content information MUST specify the "ENCODING" property parameter.
1024    Binary content information placed external to the iCalendar object
1025    MUST be referenced by a uniform resource identifier (URI).
1026
1027    The following example specifies an "ATTACH" property that references
1028    an attachment external to the iCalendar object with a URI reference:
1029
1030      ATTACH:http://xyz.com/public/quarterly-report.doc
1031
1032    The following example specifies an "ATTACH" property with inline
1033    binary encoded content information:
1034
1035      ATTACH;FMTTYPE=image/basic;ENCODING=BASE64;VALUE=BINARY:
1036       MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQAwdzELMAkGA1U
1037       EBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENvbW11bmljYXRpb25zIE
1038         &lt;...remainder of "BASE64" encoded binary data...&gt;
1039
1040 <span class="h4"><h4><a name="section-4.1.4">4.1.4</a> Character Set</h4></span>
1041
1042    There is not a property parameter to declare the character set used
1043    in a property value. The default character set for an iCalendar
1044    object is UTF-8 as defined in [<a href="http://tools.ietf.org/html/rfc2279" title="&quot;UTF-8, a transformation format of ISO 10646&quot;">RFC 2279</a>].
1045
1046    The "charset" Content-Type parameter can be used in MIME transports
1047    to specify any other IANA registered character set.
1048
1049 <span class="h3"><h3><a name="section-4.2">4.2</a> Property Parameters</h3></span>
1050
1051    A property can have attributes associated with it. These "property
1052    parameters" contain meta-information about the property or the
1053    property value. Property parameters are provided to specify such
1054    information as the location of an alternate text representation for a
1055    property value, the language of a text property value, the data type
1056    of the property value and other attributes.
1057
1058    Property parameter values that contain the COLON (US-ASCII decimal
1059    58), SEMICOLON (US-ASCII decimal 59) or COMMA (US-ASCII decimal 44)
1060    character separators MUST be specified as quoted-string text values.
1061    Property parameter values MUST NOT contain the DOUBLE-QUOTE (US-ASCII
1062    decimal 22) character. The DOUBLE-QUOTE (US-ASCII decimal 22)
1063    character is used as a delimiter for parameter values that contain
1064    restricted characters or URI text. For example:
1065
1066
1067
1068
1069 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 17]</span>
1070 </pre><pre class="newpage"><a name="page-18" id="page-18" href="#page-18" class="invisible"> </a>
1071 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1072
1073
1074      DESCRIPTION;ALTREP="http://www.wiz.org":The Fall'98 Wild Wizards
1075        Conference - - Las Vegas, NV, USA
1076
1077    Property parameter values that are not in quoted strings are case
1078    insensitive.
1079
1080    The general property parameters defined by this memo are defined by
1081    the following notation:
1082
1083      parameter  = altrepparam           ; Alternate text representation
1084                 / cnparam               ; Common name
1085                 / cutypeparam           ; Calendar user type
1086                 / delfromparam          ; Delegator
1087                 / deltoparam            ; Delegatee
1088                 / dirparam              ; Directory entry
1089                 / encodingparam         ; Inline encoding
1090                 / fmttypeparam          ; Format type
1091                 / fbtypeparam           ; Free/busy time type
1092                 / languageparam         ; Language for text
1093                 / memberparam           ; Group or list membership
1094                 / partstatparam         ; Participation status
1095                 / rangeparam            ; Recurrence identifier range
1096                 / trigrelparam          ; Alarm trigger relationship
1097                 / reltypeparam          ; Relationship type
1098                 / roleparam             ; Participation role
1099                 / rsvpparam             ; RSVP expectation
1100                 / sentbyparam           ; Sent by
1101                 / tzidparam             ; Reference to time zone object
1102                 / valuetypeparam        ; Property value data type
1103                 / ianaparam
1104         ; Some other IANA registered iCalendar parameter.
1105                 / xparam
1106         ; A non-standard, experimental parameter.
1107
1108      ianaparam  = iana-token "=" param-value *("," param-value)
1109
1110      xparam     =x-name "=" param-value *("," param-value)
1111
1112 <span class="h4"><h4><a name="section-4.2.1">4.2.1</a> Alternate Text Representation</h4></span>
1113
1114    Parameter Name: ALTREP
1115
1116    Purpose: To specify an alternate text representation for the property
1117    value.
1118
1119    Format Definition: The property parameter is defined by the following
1120    notation:
1121
1122
1123
1124
1125 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 18]</span>
1126 </pre><pre class="newpage"><a name="page-19" id="page-19" href="#page-19" class="invisible"> </a>
1127 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1128
1129
1130      altrepparam        = "ALTREP" "=" DQUOTE uri DQUOTE
1131
1132    Description: The parameter specifies a URI that points to an
1133    alternate representation for a textual property value. A property
1134    specifying this parameter MUST also include a value that reflects the
1135    default representation of the text value. The individual URI
1136    parameter values MUST each be specified in a quoted-string.
1137
1138    Example:
1139
1140      DESCRIPTION;ALTREP="CID:&lt;part3.msg.970415T083000@host.com&gt;":Project
1141        XYZ Review Meeting will include the following agenda items: (a)
1142        Market Overview, (b) Finances, (c) Project Management
1143
1144    The "ALTREP" property parameter value might point to a "text/html"
1145    content portion.
1146
1147      Content-Type:text/html
1148      Content-Id:&lt;part3.msg.970415T083000@host.com&gt;
1149
1150      &lt;html&gt;&lt;body&gt;
1151      &lt;p&gt;&lt;b&gt;Project XYZ Review Meeting&lt;/b&gt; will include the following
1152      agenda items:&lt;ol&gt;&lt;li&gt;Market
1153      Overview&lt;/li&gt;&lt;li&gt;Finances&lt;/li&gt;&lt;li&gt;Project Management&lt;/li&gt;&lt;/ol&gt;&lt;/p&gt;
1154      &lt;/body&gt;&lt;/html&gt;
1155
1156 <span class="h4"><h4><a name="section-4.2.2">4.2.2</a> Common Name</h4></span>
1157
1158    Parameter Name: CN
1159
1160    Purpose: To specify the common name to be associated with the
1161    calendar user specified by the property.
1162
1163    Format Definition: The property parameter is defined by the following
1164    notation:
1165
1166      cnparam    = "CN" "=" param-value
1167
1168    Description: This parameter can be specified on properties with a
1169    CAL-ADDRESS value type. The parameter specifies the common name to be
1170    associated with the calendar user specified by the property. The
1171    parameter value is text. The parameter value can be used for display
1172    text to be associated with the calendar address specified by the
1173    property.
1174
1175
1176
1177
1178
1179
1180
1181 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 19]</span>
1182 </pre><pre class="newpage"><a name="page-20" id="page-20" href="#page-20" class="invisible"> </a>
1183 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1184
1185
1186    Example:
1187
1188      ORGANIZER;CN="John Smith":MAILTO:jsmith@host.com
1189
1190 <span class="h4"><h4><a name="section-4.2.3">4.2.3</a> Calendar User Type</h4></span>
1191
1192    Parameter Name: CUTYPE
1193
1194    Purpose: To specify the type of calendar user specified by the
1195    property.
1196
1197    Format Definition: The property parameter is defined by the following
1198    notation:
1199
1200      cutypeparam        = "CUTYPE" "="
1201                          ("INDIVIDUAL"          ; An individual
1202                         / "GROUP"               ; A group of individuals
1203                         / "RESOURCE"            ; A physical resource
1204                         / "ROOM"                ; A room resource
1205                         / "UNKNOWN"             ; Otherwise not known
1206                         / x-name                ; Experimental type
1207                         / iana-token)           ; Other IANA registered
1208                                                 ; type
1209      ; Default is INDIVIDUAL
1210
1211    Description: This parameter can be specified on properties with a
1212    CAL-ADDRESS value type. The parameter identifies the type of calendar
1213    user specified by the property. If not specified on a property that
1214    allows this parameter, the default is INDIVIDUAL.
1215
1216    Example:
1217
1218      ATTENDEE;CUTYPE=GROUP:MAILTO:ietf-calsch@imc.org
1219
1220 <span class="h4"><h4><a name="section-4.2.4">4.2.4</a> Delegators</h4></span>
1221
1222    Parameter Name: DELEGATED-FROM
1223
1224    Purpose: To specify the calendar users that have delegated their
1225    participation to the calendar user specified by the property.
1226
1227    Format Definition: The property parameter is defined by the following
1228    notation:
1229
1230      delfromparam       = "DELEGATED-FROM" "=" DQUOTE cal-address DQUOTE
1231                           *("," DQUOTE cal-address DQUOTE)
1232
1233
1234
1235
1236
1237 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 20]</span>
1238 </pre><pre class="newpage"><a name="page-21" id="page-21" href="#page-21" class="invisible"> </a>
1239 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1240
1241
1242    Description: This parameter can be specified on properties with a
1243    CAL-ADDRESS value type. This parameter can be specified on a property
1244    that has a value type of calendar address. This parameter specifies
1245    those calendar uses that have delegated their participation in a
1246    group scheduled event or to-do to the calendar user specified by the
1247    property. The value MUST be a MAILTO URI as defined in [<a href="http://tools.ietf.org/html/rfc1738" title="&quot;Uniform Resource Locators (URL)&quot;">RFC 1738</a>].
1248    The individual calendar address parameter values MUST each be
1249    specified in a quoted-string.
1250
1251    Example:
1252
1253      ATTENDEE;DELEGATED-FROM="MAILTO:jsmith@host.com":MAILTO:
1254       jdoe@host.com
1255
1256 <span class="h4"><h4><a name="section-4.2.5">4.2.5</a> Delegatees</h4></span>
1257
1258    Parameter Name: DELEGATED-TO
1259
1260    Purpose: To specify the calendar users to whom the calendar user
1261    specified by the property has delegated participation.
1262
1263    Format Definition: The property parameter is defined by the following
1264    notation:
1265
1266      deltoparam = "DELEGATED-TO" "=" DQUOTE cal-address DQUOTE
1267                   *("," DQUOTE cal-address DQUOTE)
1268
1269    Description: This parameter can be specified on properties with a
1270    CAL-ADDRESS value type. This parameter specifies those calendar users
1271    whom have been delegated participation in a group scheduled event or
1272    to-do by the calendar user specified by the property. The value MUST
1273    be a MAILTO URI as defined in [<a href="http://tools.ietf.org/html/rfc1738" title="&quot;Uniform Resource Locators (URL)&quot;">RFC 1738</a>]. The individual calendar
1274    address parameter values MUST each be specified in a quoted-string.
1275
1276    Example:
1277
1278      ATTENDEE;DELEGATED-TO="MAILTO:jdoe@host.com","MAILTO:jqpublic@
1279       host.com":MAILTO:jsmith@host.com
1280
1281 <span class="h4"><h4><a name="section-4.2.6">4.2.6</a> Directory Entry Reference</h4></span>
1282
1283    Parameter Name: DIR
1284
1285    Purpose: To specify reference to a directory entry associated with
1286    the calendar user specified by the property.
1287
1288    Format Definition: The property parameter is defined by the following
1289    notation:
1290
1291
1292
1293 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 21]</span>
1294 </pre><pre class="newpage"><a name="page-22" id="page-22" href="#page-22" class="invisible"> </a>
1295 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1296
1297
1298      dirparam   = "DIR" "=" DQUOTE uri DQUOTE
1299
1300    Description: This parameter can be specified on properties with a
1301    CAL-ADDRESS value type. The parameter specifies a reference to the
1302    directory entry associated with the calendar user specified by the
1303    property. The parameter value is a URI. The individual URI parameter
1304    values MUST each be specified in a quoted-string.
1305
1306    Example:
1307
1308      ORGANIZER;DIR="ldap://host.com:6666/o=eDABC%20Industries,c=3DUS??
1309       (cn=3DBJim%20Dolittle)":MAILTO:jimdo@host1.com
1310
1311 <span class="h4"><h4><a name="section-4.2.7">4.2.7</a> Inline Encoding</h4></span>
1312
1313    Parameter Name: ENCODING
1314
1315    Purpose: To specify an alternate inline encoding for the property
1316    value.
1317
1318    Format Definition: The property parameter is defined by the following
1319    notation:
1320
1321      encodingparam      = "ENCODING" "="
1322                           ("8BIT"
1323         ; "8bit" text encoding is defined in [<a href="http://tools.ietf.org/html/rfc2045" title="&quot; Multipurpose Internet Mail Extensions (MIME) - Part One: Format of Internet Message Bodies&quot;">RFC 2045</a>]
1324                         / "BASE64"
1325         ; "BASE64" binary encoding format is defined in [<a href="http://tools.ietf.org/html/rfc2045" title="&quot; Multipurpose Internet Mail Extensions (MIME) - Part One: Format of Internet Message Bodies&quot;">RFC 2045</a>]
1326                         / iana-token
1327         ; Some other IANA registered iCalendar encoding type
1328                         / x-name)
1329         ; A non-standard, experimental encoding type
1330
1331    Description: The property parameter identifies the inline encoding
1332    used in a property value. The default encoding is "8BIT",
1333    corresponding to a property value consisting of text. The "BASE64"
1334    encoding type corresponds to a property value encoded using the
1335    "BASE64" encoding defined in [<a href="http://tools.ietf.org/html/rfc2045" title="&quot; Multipurpose Internet Mail Extensions (MIME) - Part One: Format of Internet Message Bodies&quot;">RFC 2045</a>].
1336
1337    If the value type parameter is ";VALUE=BINARY", then the inline
1338    encoding parameter MUST be specified with the value
1339    ";ENCODING=BASE64".
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 22]</span>
1350 </pre><pre class="newpage"><a name="page-23" id="page-23" href="#page-23" class="invisible"> </a>
1351 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1352
1353
1354    Example:
1355
1356      ATTACH;FMTYPE=IMAGE/JPEG;ENCODING=BASE64;VALUE=BINARY:MIICajC
1357       CAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQAwdzELMAkGA1UEBhMCVVMxLDA
1358       qBgNVBAoTI05ldHNjYXBlIENvbW11bmljYXRpb25zIENvcnBvcmF0aW9uMRw
1359       &lt;...remainder of "BASE64" encoded binary data...&gt;
1360
1361 <span class="h4"><h4><a name="section-4.2.8">4.2.8</a> Format Type</h4></span>
1362
1363    Parameter Name: FMTTYPE
1364
1365    Purpose: To specify the content type of a referenced object.
1366
1367    Format Definition: The property parameter is defined by the following
1368    notation:
1369
1370      fmttypeparam       = "FMTTYPE" "=" iana-token
1371                                         ; A IANA registered content type
1372                                      / x-name
1373                                         ; A non-standard content type
1374
1375    Description: This parameter can be specified on properties that are
1376    used to reference an object. The parameter specifies the content type
1377    of the referenced object. For example, on the "ATTACH" property, a
1378    FTP type URI value does not, by itself, necessarily convey the type
1379    of content associated with the resource. The parameter value MUST be
1380    the TEXT for either an IANA registered content type or a non-standard
1381    content type.
1382
1383      Example:
1384
1385       ATTACH;FMTTYPE=application/binary:ftp://domain.com/pub/docs/
1386        agenda.doc
1387
1388 <span class="h4"><h4><a name="section-4.2.9">4.2.9</a> Free/Busy Time Type</h4></span>
1389
1390    Parameter Name: FBTYPE
1391
1392    Purpose: To specify the free or busy time type.
1393
1394    Format Definition: The property parameter is defined by the following
1395    notation:
1396
1397      fbtypeparam        = "FBTYPE" "=" ("FREE" / "BUSY"
1398                         / "BUSY-UNAVAILABLE" / "BUSY-TENTATIVE"
1399                         / x-name
1400         ; Some experimental iCalendar data type.
1401                         / iana-token)
1402
1403
1404
1405 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 23]</span>
1406 </pre><pre class="newpage"><a name="page-24" id="page-24" href="#page-24" class="invisible"> </a>
1407 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1408
1409
1410         ; Some other IANA registered iCalendar data type.
1411
1412    Description: The parameter specifies the free or busy time type. The
1413    value FREE indicates that the time interval is free for scheduling.
1414    The value BUSY indicates that the time interval is busy because one
1415    or more events have been scheduled for that interval. The value
1416    BUSY-UNAVAILABLE indicates that the time interval is busy and that
1417    the interval can not be scheduled. The value BUSY-TENTATIVE indicates
1418    that the time interval is busy because one or more events have been
1419    tentatively scheduled for that interval. If not specified on a
1420    property that allows this parameter, the default is BUSY.
1421
1422    Example: The following is an example of this parameter on a FREEBUSY
1423    property.
1424
1425      FREEBUSY;FBTYPE=BUSY:19980415T133000Z/19980415T170000Z
1426
1427 <span class="h4"><h4><a name="section-4.2.10">4.2.10</a> Language</h4></span>
1428
1429    Parameter Name: LANGUAGE
1430
1431    Purpose: To specify the language for text values in a property or
1432    property parameter.
1433
1434    Format Definition: The property parameter is defined by the following
1435    notation:
1436
1437      languageparam =    "LANGUAGE" "=" language
1438
1439      language = &lt;Text identifying a language, as defined in [<a href="http://tools.ietf.org/html/rfc1766" title="&quot;Tags for the Identification of Languages&quot;">RFC 1766</a>]&gt;
1440
1441    Description: This parameter can be specified on properties with a
1442    text value type. The parameter identifies the language of the text in
1443    the property or property parameter value. The value of the "language"
1444    property parameter is that defined in [<a href="http://tools.ietf.org/html/rfc1766" title="&quot;Tags for the Identification of Languages&quot;">RFC 1766</a>].
1445
1446    For transport in a MIME entity, the Content-Language header field can
1447    be used to set the default language for the entire body part.
1448    Otherwise, no default language is assumed.
1449
1450    Example:
1451
1452      SUMMARY;LANGUAGE=us-EN:Company Holiday Party
1453
1454      LOCATION;LANGUAGE=en:Germany
1455      LOCATION;LANGUAGE=no:Tyskland
1456
1457
1458
1459
1460
1461 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 24]</span>
1462 </pre><pre class="newpage"><a name="page-25" id="page-25" href="#page-25" class="invisible"> </a>
1463 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1464
1465
1466    The following example makes use of the Quoted-Printable encoding in
1467    order to represent non-ASCII characters.
1468
1469      LOCATION;LANGUAGE=da:K=F8benhavn
1470      LOCATION;LANGUAGE=en:Copenhagen
1471
1472 <span class="h4"><h4><a name="section-4.2.11">4.2.11</a>  Group or List Membership</h4></span>
1473
1474    Parameter Name: MEMBER
1475
1476    Purpose: To specify the group or list membership of the calendar user
1477    specified by the property.
1478
1479    Format Definition: The property parameter is defined by the following
1480    notation:
1481
1482      memberparam        = "MEMBER" "=" DQUOTE cal-address DQUOTE
1483                           *("," DQUOTE cal-address DQUOTE)
1484
1485    Description: This parameter can be specified on properties with a
1486    CAL-ADDRESS value type. The parameter identifies the groups or list
1487    membership for the calendar user specified by the property. The
1488    parameter value either a single calendar address in a quoted-string
1489    or a COMMA character (US-ASCII decimal 44) list of calendar
1490    addresses, each in a quoted-string. The individual calendar address
1491    parameter values MUST each be specified in a quoted-string.
1492
1493    Example:
1494
1495      ATTENDEE;MEMBER="MAILTO:ietf-calsch@imc.org":MAILTO:jsmith@host.com
1496
1497      ATTENDEE;MEMBER="MAILTO:projectA@host.com","MAILTO:projectB@host.
1498       com":MAILTO:janedoe@host.com
1499
1500 <span class="h4"><h4><a name="section-4.2.12">4.2.12</a> Participation Status</h4></span>
1501
1502    Parameter Name: PARTSTAT
1503
1504    Purpose: To specify the participation status for the calendar user
1505    specified by the property.
1506
1507    Format Definition: The property parameter is defined by the following
1508    notation:
1509
1510      partstatparam      = "PARTSTAT" "="
1511                          ("NEEDS-ACTION"        ; Event needs action
1512                         / "ACCEPTED"            ; Event accepted
1513                         / "DECLINED"            ; Event declined
1514
1515
1516
1517 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 25]</span>
1518 </pre><pre class="newpage"><a name="page-26" id="page-26" href="#page-26" class="invisible"> </a>
1519 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1520
1521
1522                         / "TENTATIVE"           ; Event tentatively
1523                                                 ; accepted
1524                         / "DELEGATED"           ; Event delegated
1525                         / x-name                ; Experimental status
1526                         / iana-token)           ; Other IANA registered
1527                                                 ; status
1528      ; These are the participation statuses for a "VEVENT". Default is
1529      ; NEEDS-ACTION
1530      partstatparam      /= "PARTSTAT" "="
1531                          ("NEEDS-ACTION"        ; To-do needs action
1532                         / "ACCEPTED"            ; To-do accepted
1533                         / "DECLINED"            ; To-do declined
1534                         / "TENTATIVE"           ; To-do tentatively
1535                                                 ; accepted
1536                         / "DELEGATED"           ; To-do delegated
1537                         / "COMPLETED"           ; To-do completed.
1538                                                 ; COMPLETED property has
1539                                                 ;date/time completed.
1540                         / "IN-PROCESS"          ; To-do in process of
1541                                                 ; being completed
1542                         / x-name                ; Experimental status
1543                         / iana-token)           ; Other IANA registered
1544                                                 ; status
1545      ; These are the participation statuses for a "VTODO". Default is
1546      ; NEEDS-ACTION
1547
1548      partstatparam      /= "PARTSTAT" "="
1549                          ("NEEDS-ACTION"        ; Journal needs action
1550                         / "ACCEPTED"            ; Journal accepted
1551                         / "DECLINED"            ; Journal declined
1552                         / x-name                ; Experimental status
1553                         / iana-token)           ; Other IANA registered
1554                                                 ; status
1555      ; These are the participation statuses for a "VJOURNAL". Default is
1556      ; NEEDS-ACTION
1557
1558    Description: This parameter can be specified on properties with a
1559    CAL-ADDRESS value type. The parameter identifies the participation
1560    status for the calendar user specified by the property value. The
1561    parameter values differ depending on whether they are associated with
1562    a group scheduled "VEVENT", "VTODO" or "VJOURNAL". The values MUST
1563    match one of the values allowed for the given calendar component. If
1564    not specified on a property that allows this parameter, the default
1565    value is NEEDS-ACTION.
1566
1567    Example:
1568
1569      ATTENDEE;PARTSTAT=DECLINED:MAILTO:jsmith@host.com
1570
1571
1572
1573 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 26]</span>
1574 </pre><pre class="newpage"><a name="page-27" id="page-27" href="#page-27" class="invisible"> </a>
1575 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1576
1577
1578 <span class="h4"><h4><a name="section-4.2.13">4.2.13</a>  Recurrence Identifier Range</h4></span>
1579
1580    Parameter Name: RANGE
1581
1582    Purpose: To specify the effective range of recurrence instances from
1583    the instance specified by the recurrence identifier specified by the
1584    property.
1585
1586    Format Definition: The property parameter is defined by the following
1587    notation:
1588
1589      rangeparam = "RANGE" "=" ("THISANDPRIOR"
1590         ; To specify all instances prior to the recurrence identifier
1591                 / "THISANDFUTURE")
1592         ; To specify the instance specified by the recurrence identifier
1593         ; and all subsequent recurrence instances
1594
1595    Description: The parameter can be specified on a property that
1596    specifies a recurrence identifier. The parameter specifies the
1597    effective range of recurrence instances that is specified by the
1598    property. The effective range is from the recurrence identified
1599    specified by the property. If this parameter is not specified an
1600    allowed property, then the default range is the single instance
1601    specified by the recurrence identifier value of the property. The
1602    parameter value can be "THISANDPRIOR" to indicate a range defined by
1603    the recurrence identified value of the property and all prior
1604    instances. The parameter value can also be "THISANDFUTURE" to
1605    indicate a range defined by the recurrence identifier and all
1606    subsequent instances.
1607
1608    Example:
1609
1610      RECURRENCE-ID;RANGE=THISANDPRIOR:19980401T133000Z
1611
1612 <span class="h4"><h4><a name="section-4.2.14">4.2.14</a> Alarm Trigger Relationship</h4></span>
1613
1614    Parameter Name: RELATED
1615
1616    Purpose: To specify the relationship of the alarm trigger with
1617    respect to the start or end of the calendar component.
1618
1619    Format Definition: The property parameter is defined by the following
1620    notation:
1621
1622      trigrelparam       = "RELATED" "="
1623                          ("START"       ; Trigger off of start
1624                         / "END")        ; Trigger off of end
1625
1626
1627
1628
1629 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 27]</span>
1630 </pre><pre class="newpage"><a name="page-28" id="page-28" href="#page-28" class="invisible"> </a>
1631 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1632
1633
1634    Description: The parameter can be specified on properties that
1635    specify an alarm trigger with a DURATION value type. The parameter
1636    specifies whether the alarm will trigger relative to the start or end
1637    of the calendar component. The parameter value START will set the
1638    alarm to trigger off the start of the calendar component; the
1639    parameter value END will set the alarm to trigger off the end of the
1640    calendar component. If the parameter is not specified on an allowable
1641    property, then the default is START.
1642
1643    Example:
1644
1645      TRIGGER;RELATED=END:PT5M
1646
1647 <span class="h4"><h4><a name="section-4.2.15">4.2.15</a> Relationship Type</h4></span>
1648
1649    Parameter Name: RELTYPE
1650
1651    Purpose: To specify the type of hierarchical relationship associated
1652    with the calendar component specified by the property.
1653
1654    Format Definition: The property parameter is defined by the following
1655    notation:
1656
1657      reltypeparam       = "RELTYPE" "="
1658                          ("PARENT"      ; Parent relationship. Default.
1659                         / "CHILD"       ; Child relationship
1660                         / "SIBLING      ; Sibling relationship
1661                         / iana-token    ; Some other IANA registered
1662                                         ; iCalendar relationship type
1663                         / x-name)       ; A non-standard, experimental
1664                                         ; relationship type
1665
1666    Description: This parameter can be specified on a property that
1667    references another related calendar. The parameter specifies the
1668    hierarchical relationship type of the calendar component referenced
1669    by the property. The parameter value can be PARENT, to indicate that
1670    the referenced calendar component is a superior of calendar
1671    component; CHILD to indicate that the referenced calendar component
1672    is a subordinate of the calendar component; SIBLING to indicate that
1673    the referenced calendar component is a peer of the calendar
1674    component. If this parameter is not specified on an allowable
1675    property, the default relationship type is PARENT.
1676
1677    Example:
1678
1679      RELATED-TO;RELTYPE=SIBLING:&lt;19960401-080045-4000F192713@host.com&gt;
1680
1681
1682
1683
1684
1685 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 28]</span>
1686 </pre><pre class="newpage"><a name="page-29" id="page-29" href="#page-29" class="invisible"> </a>
1687 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1688
1689
1690 <span class="h4"><h4><a name="section-4.2.16">4.2.16</a> Participation Role</h4></span>
1691
1692    Parameter Name: ROLE
1693
1694    Purpose: To specify the participation role for the calendar user
1695    specified by the property.
1696
1697    Format Definition: The property parameter is defined by the following
1698    notation:
1699
1700      roleparam  = "ROLE" "="
1701                  ("CHAIR"               ; Indicates chair of the
1702                                         ; calendar entity
1703                 / "REQ-PARTICIPANT"     ; Indicates a participant whose
1704                                         ; participation is required
1705                 / "OPT-PARTICIPANT"     ; Indicates a participant whose
1706                                         ; participation is optional
1707                 / "NON-PARTICIPANT"     ; Indicates a participant who is
1708                                         ; copied for information
1709                                         ; purposes only
1710                 / x-name                ; Experimental role
1711                 / iana-token)           ; Other IANA role
1712      ; Default is REQ-PARTICIPANT
1713
1714    Description: This parameter can be specified on properties with a
1715    CAL-ADDRESS value type. The parameter specifies the participation
1716    role for the calendar user specified by the property in the group
1717    schedule calendar component. If not specified on a property that
1718    allows this parameter, the default value is REQ-PARTICIPANT.
1719
1720    Example:
1721
1722      ATTENDEE;ROLE=CHAIR:MAILTO:mrbig@host.com
1723
1724 <span class="h4"><h4><a name="section-4.2.17">4.2.17</a>  RSVP Expectation</h4></span>
1725
1726    Parameter Name: RSVP
1727
1728    Purpose: To specify whether there is an expectation of a favor of a
1729    reply from the calendar user specified by the property value.
1730
1731    Format Definition: The property parameter is defined by the following
1732    notation:
1733
1734      rsvpparam = "RSVP" "=" ("TRUE" / "FALSE")
1735      ; Default is FALSE
1736
1737
1738
1739
1740
1741 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 29]</span>
1742 </pre><pre class="newpage"><a name="page-30" id="page-30" href="#page-30" class="invisible"> </a>
1743 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1744
1745
1746    Description: This parameter can be specified on properties with a
1747    CAL-ADDRESS value type. The parameter identifies the expectation of a
1748    reply from the calendar user specified by the property value. This
1749    parameter is used by the "Organizer" to request a participation
1750    status reply from an "Attendee" of a group scheduled event or to-do.
1751    If not specified on a property that allows this parameter, the
1752    default value is FALSE.
1753
1754    Example:
1755
1756      ATTENDEE;RSVP=TRUE:MAILTO:jsmith@host.com
1757
1758 <span class="h4"><h4><a name="section-4.2.18">4.2.18</a>  Sent By</h4></span>
1759
1760    Parameter Name: SENT-BY
1761
1762    Purpose: To specify the calendar user that is acting on behalf of the
1763    calendar user specified by the property.
1764
1765    Format Definition: The property parameter is defined by the following
1766    notation:
1767
1768      sentbyparam        = "SENT-BY" "=" DQUOTE cal-address DQUOTE
1769
1770    Description: This parameter can be specified on properties with a
1771    CAL-ADDRESS value type. The parameter specifies the calendar user
1772    that is acting on behalf of the calendar user specified by the
1773    property. The parameter value MUST be a MAILTO URI as defined in [RFC
1774    1738]. The individual calendar address parameter values MUST each be
1775    specified in a quoted-string.
1776
1777    Example:
1778
1779      ORGANIZER;SENT-BY:"MAILTO:sray@host.com":MAILTO:jsmith@host.com
1780
1781 <span class="h4"><h4><a name="section-4.2.19">4.2.19</a> Time Zone Identifier</h4></span>
1782
1783    Parameter Name: TZID
1784
1785    Purpose: To specify the identifier for the time zone definition for a
1786    time component in the property value.
1787
1788    Format Definition: This property parameter is defined by the
1789    following notation:
1790
1791      tzidparam  = "TZID" "=" [<a href="#ref-tzidprefix">tzidprefix</a>] paramtext CRLF
1792
1793      tzidprefix = "/"
1794
1795
1796
1797 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 30]</span>
1798 </pre><pre class="newpage"><a name="page-31" id="page-31" href="#page-31" class="invisible"> </a>
1799 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1800
1801
1802    Description: The parameter MUST be specified on the "DTSTART",
1803    "DTEND", "DUE", "EXDATE" and "RDATE" properties when either a DATE-
1804    TIME or TIME value type is specified and when the value is not either
1805    a UTC or a "floating" time. Refer to the DATE-TIME or TIME value type
1806    definition for a description of UTC and "floating time" formats. This
1807    property parameter specifies a text value which uniquely identifies
1808    the "VTIMEZONE" calendar component to be used when evaluating the
1809    time portion of the property. The value of the TZID property
1810    parameter will be equal to the value of the TZID property for the
1811    matching time zone definition. An individual "VTIMEZONE" calendar
1812    component MUST be specified for each unique "TZID" parameter value
1813    specified in the iCalendar object.
1814
1815    The parameter MUST be specified on properties with a DATE-TIME value
1816    if the DATE-TIME is not either a UTC or a "floating" time.
1817
1818    The presence of the SOLIDUS character (US-ASCII decimal 47) as a
1819    prefix, indicates that this TZID represents a unique ID in a globally
1820    defined time zone registry (when such registry is defined).
1821
1822         Note: This document does not define a naming convention for time
1823         zone identifiers. Implementers may want to use the naming
1824         conventions defined in existing time zone specifications such as
1825         the public-domain Olson database [<a href="#ref-TZ" title="&quot;ftp://elsie.nci.nih.gov/pub/&quot;">TZ</a>]. The specification of
1826         globally unique time zone identifiers is not addressed by this
1827         document and is left for future study.
1828
1829    The following are examples of this property parameter:
1830
1831      DTSTART;TZID=US-Eastern:19980119T020000
1832
1833      DTEND;TZID=US-Eastern:19980119T030000
1834
1835    The TZID property parameter MUST NOT be applied to DATE-TIME or TIME
1836    properties whose time values are specified in UTC.
1837
1838    The use of local time in a DATE-TIME or TIME value without the TZID
1839    property parameter is to be interpreted as a local time value,
1840    regardless of the existence of "VTIMEZONE" calendar components in the
1841    iCalendar object.
1842
1843    For more information see the sections on the data types DATE-TIME and
1844    TIME.
1845
1846
1847
1848
1849
1850
1851
1852
1853 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 31]</span>
1854 </pre><pre class="newpage"><a name="page-32" id="page-32" href="#page-32" class="invisible"> </a>
1855 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1856
1857
1858 <span class="h4"><h4><a name="section-4.2.20">4.2.20</a> Value Data Types</h4></span>
1859
1860    Parameter Name: VALUE
1861
1862    Purpose: To explicitly specify the data type format for a property
1863    value.
1864
1865    Format Definition: The "VALUE" property parameter is defined by the
1866    following notation:
1867
1868      valuetypeparam = "VALUE" "=" valuetype
1869
1870      valuetype  = ("BINARY"
1871                 / "BOOLEAN"
1872                 / "CAL-ADDRESS"
1873                 / "DATE"
1874                 / "DATE-TIME"
1875                 / "DURATION"
1876                 / "FLOAT"
1877                 / "INTEGER"
1878                 / "PERIOD"
1879                 / "RECUR"
1880                 / "TEXT"
1881                 / "TIME"
1882                 / "URI"
1883                 / "UTC-OFFSET"
1884                 / x-name
1885                 ; Some experimental iCalendar data type.
1886                 / iana-token)
1887                 ; Some other IANA registered iCalendar data type.
1888
1889    Description: The parameter specifies the data type and format of the
1890    property value. The property values MUST be of a single value type.
1891    For example, a "RDATE" property cannot have a combination of DATE-
1892    TIME and TIME value types.
1893
1894    If the property's value is the default value type, then this
1895    parameter need not be specified. However, if the property's default
1896    value type is overridden by some other allowable value type, then
1897    this parameter MUST be specified.
1898
1899 <span class="h3"><h3><a name="section-4.3">4.3</a> Property Value Data Types</h3></span>
1900
1901    The properties in an iCalendar object are strongly typed. The
1902    definition of each property restricts the value to be one of the
1903    value data types, or simply value types, defined in this section. The
1904    value type for a property will either be specified implicitly as the
1905    default value type or will be explicitly specified with the "VALUE"
1906
1907
1908
1909 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 32]</span>
1910 </pre><pre class="newpage"><a name="page-33" id="page-33" href="#page-33" class="invisible"> </a>
1911 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1912
1913
1914    parameter. If the value type of a property is one of the alternate
1915    valid types, then it MUST be explicitly specified with the "VALUE"
1916    parameter.
1917
1918 <span class="h4"><h4><a name="section-4.3.1">4.3.1</a>   Binary</h4></span>
1919
1920    Value Name: BINARY
1921
1922    Purpose: This value type is used to identify properties that contain
1923    a character encoding of inline binary data. For example, an inline
1924    attachment of an object code might be included in an iCalendar
1925    object.
1926
1927    Formal Definition: The value type is defined by the following
1928    notation:
1929
1930      binary     = *(4b-char) [<a href="#ref-b-end">b-end</a>]
1931      ; A "BASE64" encoded character string, as defined by [<a href="http://tools.ietf.org/html/rfc2045" title="&quot; Multipurpose Internet Mail Extensions (MIME) - Part One: Format of Internet Message Bodies&quot;">RFC 2045</a>].
1932
1933      b-end      = (2b-char "==") / (3b-char "=")
1934
1935      b-char = ALPHA / DIGIT / "+" / "/"
1936
1937    Description: Property values with this value type MUST also include
1938    the inline encoding parameter sequence of ";ENCODING=BASE64". That
1939    is, all inline binary data MUST first be character encoded using the
1940    "BASE64" encoding method defined in [<a href="http://tools.ietf.org/html/rfc2045" title="&quot; Multipurpose Internet Mail Extensions (MIME) - Part One: Format of Internet Message Bodies&quot;">RFC 2045</a>]. No additional content
1941    value encoding (i.e., BACKSLASH character encoding) is defined for
1942    this value type.
1943
1944    Example: The following is an abridged example of a "BASE64" encoded
1945    binary value data.
1946
1947      ATTACH;VALUE=BINARY;ENCODING=BASE64:MIICajCCAdOgAwIBAgICBEUwDQY
1948       JKoZIhvcNAQEEBQAwdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlI
1949       ENvbW11bmljYXRpb25zIENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZv
1950         &lt;...remainder of "BASE64" encoded binary data...&gt;
1951
1952 <span class="h4"><h4><a name="section-4.3.2">4.3.2</a>   Boolean</h4></span>
1953
1954    Value Name: BOOLEAN
1955
1956    Purpose: This value type is used to identify properties that contain
1957    either a "TRUE" or "FALSE" Boolean value.
1958
1959    Formal Definition: The value type is defined by the following
1960    notation:
1961
1962
1963
1964
1965 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 33]</span>
1966 </pre><pre class="newpage"><a name="page-34" id="page-34" href="#page-34" class="invisible"> </a>
1967 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
1968
1969
1970      boolean    = "TRUE" / "FALSE"
1971
1972    Description: These values are case insensitive text. No additional
1973    content value encoding (i.e., BACKSLASH character encoding) is
1974    defined for this value type.
1975
1976    Example: The following is an example of a hypothetical property that
1977    has a BOOLEAN value type:
1978
1979    GIBBERISH:TRUE
1980
1981 <span class="h4"><h4><a name="section-4.3.3">4.3.3</a>   Calendar User Address</h4></span>
1982
1983    Value Name: CAL-ADDRESS
1984
1985    Purpose: This value type is used to identify properties that contain
1986    a calendar user address.
1987
1988    Formal Definition: The value type is as defined by the following
1989    notation:
1990
1991      cal-address        = uri
1992
1993    Description: The value is a URI as defined by [<a href="http://tools.ietf.org/html/rfc1738" title="&quot;Uniform Resource Locators (URL)&quot;">RFC 1738</a>] or any other
1994    IANA registered form for a URI. When used to address an Internet
1995    email transport address for a calendar user, the value MUST be a
1996    MAILTO URI, as defined by [<a href="http://tools.ietf.org/html/rfc1738" title="&quot;Uniform Resource Locators (URL)&quot;">RFC 1738</a>]. No additional content value
1997    encoding (i.e., BACKSLASH character encoding) is defined for this
1998    value type.
1999
2000    Example:
2001
2002      ATTENDEE:MAILTO:jane_doe@host.com
2003
2004 <span class="h4"><h4><a name="section-4.3.4">4.3.4</a> Date</h4></span>
2005
2006    Value Name: DATE
2007
2008    Purpose: This value type is used to identify values that contain a
2009    calendar date.
2010
2011    Formal Definition: The value type is defined by the following
2012    notation:
2013
2014      date               = date-value
2015
2016      date-value         = date-fullyear date-month date-mday
2017      date-fullyear      = 4DIGIT
2018
2019
2020
2021 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 34]</span>
2022 </pre><pre class="newpage"><a name="page-35" id="page-35" href="#page-35" class="invisible"> </a>
2023 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2024
2025
2026      date-month         = 2DIGIT        ;01-12
2027      date-mday          = 2DIGIT        ;01-28, 01-29, 01-30, 01-31
2028                                         ;based on month/year
2029
2030    Description: If the property permits, multiple "date" values are
2031    specified as a COMMA character (US-ASCII decimal 44) separated list
2032    of values. The format for the value type is expressed as the [ISO
2033    8601] complete representation, basic format for a calendar date. The
2034    textual format specifies a four-digit year, two-digit month, and
2035    two-digit day of the month. There are no separator characters between
2036    the year, month and day component text.
2037
2038    No additional content value encoding (i.e., BACKSLASH character
2039    encoding) is defined for this value type.
2040
2041    Example: The following represents July 14, 1997:
2042
2043      19970714
2044
2045 <span class="h4"><h4><a name="section-4.3.5">4.3.5</a>   Date-Time</h4></span>
2046
2047    Value Name: DATE-TIME
2048
2049    Purpose: This value type is used to identify values that specify a
2050    precise calendar date and time of day.
2051
2052    Formal Definition: The value type is defined by the following
2053    notation:
2054
2055      date-time  = date "T" time ;As specified in the date and time
2056                                 ;value definitions
2057
2058    Description: If the property permits, multiple "date-time" values are
2059    specified as a COMMA character (US-ASCII decimal 44) separated list
2060    of values. No additional content value encoding (i.e., BACKSLASH
2061    character encoding) is defined for this value type.
2062
2063    The "DATE-TIME" data type is used to identify values that contain a
2064    precise calendar date and time of day. The format is based on the
2065    [ISO 8601] complete representation, basic format for a calendar date
2066    and time of day. The text format is a concatenation of the "date",
2067    followed by the LATIN CAPITAL LETTER T character (US-ASCII decimal
2068    84) time designator, followed by the "time" format.
2069
2070    The "DATE-TIME" data type expresses time values in three forms:
2071
2072    The form of date and time with UTC offset MUST NOT be used. For
2073    example, the following is not valid for a date-time value:
2074
2075
2076
2077 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 35]</span>
2078 </pre><pre class="newpage"><a name="page-36" id="page-36" href="#page-36" class="invisible"> </a>
2079 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2080
2081
2082      DTSTART:19980119T230000-0800       ;Invalid time format
2083
2084    FORM #1: DATE WITH LOCAL TIME
2085
2086    The date with local time form is simply a date-time value that does
2087    not contain the UTC designator nor does it reference a time zone. For
2088    example, the following represents Janurary 18, 1998, at 11 PM:
2089
2090      DTSTART:19980118T230000
2091
2092    Date-time values of this type are said to be "floating" and are not
2093    bound to any time zone in particular. They are used to represent the
2094    same hour, minute, and second value regardless of which time zone is
2095    currently being observed. For example, an event can be defined that
2096    indicates that an individual will be busy from 11:00 AM to 1:00 PM
2097    every day, no matter which time zone the person is in. In these
2098    cases, a local time can be specified. The recipient of an iCalendar
2099    object with a property value consisting of a local time, without any
2100    relative time zone information, SHOULD interpret the value as being
2101    fixed to whatever time zone the ATTENDEE is in at any given moment.
2102    This means that two ATTENDEEs, in different time zones, receiving the
2103    same event definition as a floating time, may be participating in the
2104    event at different actual times. Floating time SHOULD only be used
2105    where that is the reasonable behavior.
2106
2107    In most cases, a fixed time is desired. To properly communicate a
2108    fixed time in a property value, either UTC time or local time with
2109    time zone reference MUST be specified.
2110
2111    The use of local time in a DATE-TIME value without the TZID property
2112    parameter is to be interpreted as floating time, regardless of the
2113    existence of "VTIMEZONE" calendar components in the iCalendar object.
2114
2115    FORM #2: DATE WITH UTC TIME
2116
2117    The date with UTC time, or absolute time, is identified by a LATIN
2118    CAPITAL LETTER Z suffix character (US-ASCII decimal 90), the UTC
2119    designator, appended to the time value. For example, the following
2120    represents January 19, 1998, at 0700 UTC:
2121
2122      DTSTART:19980119T070000Z
2123
2124    The TZID property parameter MUST NOT be applied to DATE-TIME
2125    properties whose time values are specified in UTC.
2126
2127    FORM #3: DATE WITH LOCAL TIME AND TIME ZONE REFERENCE
2128
2129
2130
2131
2132
2133 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 36]</span>
2134 </pre><pre class="newpage"><a name="page-37" id="page-37" href="#page-37" class="invisible"> </a>
2135 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2136
2137
2138    The date and local time with reference to time zone information is
2139    identified by the use the TZID property parameter to reference the
2140    appropriate time zone definition. TZID is discussed in detail in the
2141    section on Time Zone. For example, the following represents 2 AM in
2142    New York on Janurary 19, 1998:
2143
2144           DTSTART;TZID=US-Eastern:19980119T020000
2145
2146    Example: The following represents July 14, 1997, at 1:30 PM in New
2147    York City in each of the three time formats, using the "DTSTART"
2148    property.
2149
2150      DTSTART:19970714T133000            ;Local time
2151      DTSTART:19970714T173000Z           ;UTC time
2152      DTSTART;TZID=US-Eastern:19970714T133000    ;Local time and time
2153                         ; zone reference
2154
2155    A time value MUST ONLY specify 60 seconds when specifying the
2156    periodic "leap second" in the time value. For example:
2157
2158      COMPLETED:19970630T235960Z
2159
2160 <span class="h4"><h4><a name="section-4.3.6">4.3.6</a>   Duration</h4></span>
2161
2162    Value Name: DURATION
2163
2164    Purpose: This value type is used to identify properties that contain
2165    a duration of time.
2166
2167    Formal Definition: The value type is defined by the following
2168    notation:
2169
2170      dur-value  = (["+"] / "-") "P" (dur-date / dur-time / dur-week)
2171
2172      dur-date   = dur-day [<a href="#ref-dur-time">dur-time</a>]
2173      dur-time   = "T" (dur-hour / dur-minute / dur-second)
2174      dur-week   = 1*DIGIT "W"
2175      dur-hour   = 1*DIGIT "H" [<a href="#ref-dur-minute">dur-minute</a>]
2176      dur-minute = 1*DIGIT "M" [<a href="#ref-dur-second">dur-second</a>]
2177      dur-second = 1*DIGIT "S"
2178      dur-day    = 1*DIGIT "D"
2179
2180    Description: If the property permits, multiple "duration" values are
2181    specified by a COMMA character (US-ASCII decimal 44) separated list
2182    of values. The format is expressed as the [ISO 8601] basic format for
2183    the duration of time. The format can represent durations in terms of
2184    weeks, days, hours, minutes, and seconds.
2185
2186
2187
2188
2189 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 37]</span>
2190 </pre><pre class="newpage"><a name="page-38" id="page-38" href="#page-38" class="invisible"> </a>
2191 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2192
2193
2194    No additional content value encoding (i.e., BACKSLASH character
2195    encoding) are defined for this value type.
2196
2197    Example: A duration of 15 days, 5 hours and 20 seconds would be:
2198
2199      P15DT5H0M20S
2200
2201    A duration of 7 weeks would be:
2202
2203      P7W
2204
2205 <span class="h4"><h4><a name="section-4.3.7">4.3.7</a>   Float</h4></span>
2206
2207    Value Name: FLOAT
2208
2209    Purpose: This value type is used to identify properties that contain
2210    a real number value.
2211
2212    Formal Definition: The value type is defined by the following
2213    notation:
2214
2215      float      = (["+"] / "-") 1*DIGIT ["." 1*DIGIT]
2216
2217    Description: If the property permits, multiple "float" values are
2218    specified by a COMMA character (US-ASCII decimal 44) separated list
2219    of values.
2220
2221    No additional content value encoding (i.e., BACKSLASH character
2222    encoding) is defined for this value type.
2223
2224    Example:
2225
2226      1000000.0000001
2227      1.333
2228      -3.14
2229
2230 <span class="h4"><h4><a name="section-4.3.8">4.3.8</a> Integer</h4></span>
2231
2232      Value Name:INTEGER
2233
2234      Purpose: This value type is used to identify properties that contain
2235      a signed integer value.
2236
2237      Formal Definition: The value type is defined by the following
2238      notation:
2239
2240      integer    = (["+"] / "-") 1*DIGIT
2241
2242
2243
2244
2245 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 38]</span>
2246 </pre><pre class="newpage"><a name="page-39" id="page-39" href="#page-39" class="invisible"> </a>
2247 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2248
2249
2250      Description: If the property permits, multiple "integer" values are
2251      specified by a COMMA character (US-ASCII decimal 44) separated list
2252      of values. The valid range for "integer" is -2147483648 to
2253      2147483647. If the sign is not specified, then the value is assumed
2254      to be positive.
2255
2256      No additional content value encoding (i.e., BACKSLASH character
2257      encoding) is defined for this value type.
2258
2259      Example:
2260
2261      1234567890
2262      -1234567890
2263      +1234567890
2264      432109876
2265
2266 <span class="h4"><h4><a name="section-4.3.9">4.3.9</a> Period of Time</h4></span>
2267
2268    Value Name: PERIOD
2269
2270    Purpose: This value type is used to identify values that contain a
2271    precise period of time.
2272
2273    Formal Definition: The data type is defined by the following
2274    notation:
2275
2276      period     = period-explicit / period-start
2277
2278      period-explicit = date-time "/" date-time
2279      ; [ISO 8601] complete representation basic format for a period of
2280      ; time consisting of a start and end. The start MUST be before the
2281      ; end.
2282
2283      period-start = date-time "/" dur-value
2284      ; [ISO 8601] complete representation basic format for a period of
2285      ; time consisting of a start and positive duration of time.
2286
2287    Description: If the property permits, multiple "period" values are
2288    specified by a COMMA character (US-ASCII decimal 44) separated list
2289    of values. There are two forms of a period of time. First, a period
2290    of time is identified by its start and its end. This format is
2291    expressed as the [ISO 8601] complete representation, basic format for
2292    "DATE-TIME" start of the period, followed by a SOLIDUS character
2293    (US-ASCII decimal 47), followed by the "DATE-TIME" of the end of the
2294    period. The start of the period MUST be before the end of the period.
2295    Second, a period of time can also be defined by a start and a
2296    positive duration of time. The format is expressed as the [ISO 8601]
2297    complete representation, basic format for the "DATE-TIME" start of
2298
2299
2300
2301 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 39]</span>
2302 </pre><pre class="newpage"><a name="page-40" id="page-40" href="#page-40" class="invisible"> </a>
2303 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2304
2305
2306    the period, followed by a SOLIDUS character (US-ASCII decimal 47),
2307    followed by the [ISO 8601] basic format for "DURATION" of the period.
2308
2309    Example: The period starting at 18:00:00 UTC, on January 1, 1997 and
2310    ending at 07:00:00 UTC on January 2, 1997 would be:
2311
2312      19970101T180000Z/19970102T070000Z
2313
2314    The period start at 18:00:00 on January 1, 1997 and lasting 5 hours
2315    and 30 minutes would be:
2316
2317      19970101T180000Z/PT5H30M
2318
2319    No additional content value encoding (i.e., BACKSLASH character
2320    encoding) is defined for this value type.
2321
2322 <span class="h4"><h4><a name="section-4.3.10">4.3.10</a> Recurrence Rule</h4></span>
2323
2324    Value Name: RECUR
2325
2326    Purpose: This value type is used to identify properties that contain
2327    a recurrence rule specification.
2328
2329    Formal Definition: The value type is defined by the following
2330    notation:
2331
2332      recur      = "FREQ"=freq *(
2333
2334                 ; either UNTIL or COUNT may appear in a 'recur',
2335                 ; but UNTIL and COUNT MUST NOT occur in the same 'recur'
2336
2337                 ( ";" "UNTIL" "=" enddate ) /
2338                 ( ";" "COUNT" "=" 1*DIGIT ) /
2339
2340                 ; the rest of these keywords are optional,
2341                 ; but MUST NOT occur more than once
2342
2343                 ( ";" "INTERVAL" "=" 1*DIGIT )          /
2344                 ( ";" "BYSECOND" "=" byseclist )        /
2345                 ( ";" "BYMINUTE" "=" byminlist )        /
2346                 ( ";" "BYHOUR" "=" byhrlist )           /
2347                 ( ";" "BYDAY" "=" bywdaylist )          /
2348                 ( ";" "BYMONTHDAY" "=" bymodaylist )    /
2349                 ( ";" "BYYEARDAY" "=" byyrdaylist )     /
2350                 ( ";" "BYWEEKNO" "=" bywknolist )       /
2351                 ( ";" "BYMONTH" "=" bymolist )          /
2352                 ( ";" "BYSETPOS" "=" bysplist )         /
2353                 ( ";" "WKST" "=" weekday )              /
2354
2355
2356
2357 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 40]</span>
2358 </pre><pre class="newpage"><a name="page-41" id="page-41" href="#page-41" class="invisible"> </a>
2359 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2360
2361
2362                 ( ";" x-name "=" text )
2363                 )
2364
2365      freq       = "SECONDLY" / "MINUTELY" / "HOURLY" / "DAILY"
2366                 / "WEEKLY" / "MONTHLY" / "YEARLY"
2367
2368      enddate    = date
2369      enddate    =/ date-time            ;An UTC value
2370
2371      byseclist  = seconds / ( seconds *("," seconds) )
2372
2373      seconds    = 1DIGIT / 2DIGIT       ;0 to 59
2374
2375      byminlist  = minutes / ( minutes *("," minutes) )
2376
2377      minutes    = 1DIGIT / 2DIGIT       ;0 to 59
2378
2379      byhrlist   = hour / ( hour *("," hour) )
2380
2381      hour       = 1DIGIT / 2DIGIT       ;0 to 23
2382
2383      bywdaylist = weekdaynum / ( weekdaynum *("," weekdaynum) )
2384
2385      weekdaynum = [([<a href="#ref-plus">plus</a>] ordwk / minus ordwk)] weekday
2386
2387      plus       = "+"
2388
2389      minus      = "-"
2390
2391      ordwk      = 1DIGIT / 2DIGIT       ;1 to 53
2392
2393      weekday    = "SU" / "MO" / "TU" / "WE" / "TH" / "FR" / "SA"
2394      ;Corresponding to SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY,
2395      ;FRIDAY, SATURDAY and SUNDAY days of the week.
2396
2397      bymodaylist = monthdaynum / ( monthdaynum *("," monthdaynum) )
2398
2399      monthdaynum = ([<a href="#ref-plus">plus</a>] ordmoday) / (minus ordmoday)
2400
2401      ordmoday   = 1DIGIT / 2DIGIT       ;1 to 31
2402
2403      byyrdaylist = yeardaynum / ( yeardaynum *("," yeardaynum) )
2404
2405      yeardaynum = ([<a href="#ref-plus">plus</a>] ordyrday) / (minus ordyrday)
2406
2407      ordyrday   = 1DIGIT / 2DIGIT / 3DIGIT      ;1 to 366
2408
2409      bywknolist = weeknum / ( weeknum *("," weeknum) )
2410
2411
2412
2413 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 41]</span>
2414 </pre><pre class="newpage"><a name="page-42" id="page-42" href="#page-42" class="invisible"> </a>
2415 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2416
2417
2418      weeknum    = ([<a href="#ref-plus">plus</a>] ordwk) / (minus ordwk)
2419
2420      bymolist   = monthnum / ( monthnum *("," monthnum) )
2421
2422      monthnum   = 1DIGIT / 2DIGIT       ;1 to 12
2423
2424      bysplist   = setposday / ( setposday *("," setposday) )
2425
2426      setposday  = yeardaynum
2427
2428    Description: If the property permits, multiple "recur" values are
2429    specified by a COMMA character (US-ASCII decimal 44) separated list
2430    of values. The value type is a structured value consisting of a list
2431    of one or more recurrence grammar parts. Each rule part is defined by
2432    a NAME=VALUE pair. The rule parts are separated from each other by
2433    the SEMICOLON character (US-ASCII decimal 59). The rule parts are not
2434    ordered in any particular sequence. Individual rule parts MUST only
2435    be specified once.
2436
2437    The FREQ rule part identifies the type of recurrence rule. This rule
2438    part MUST be specified in the recurrence rule. Valid values include
2439    SECONDLY, to specify repeating events based on an interval of a
2440    second or more; MINUTELY, to specify repeating events based on an
2441    interval of a minute or more; HOURLY, to specify repeating events
2442    based on an interval of an hour or more; DAILY, to specify repeating
2443    events based on an interval of a day or more; WEEKLY, to specify
2444    repeating events based on an interval of a week or more; MONTHLY, to
2445    specify repeating events based on an interval of a month or more; and
2446    YEARLY, to specify repeating events based on an interval of a year or
2447    more.
2448
2449    The INTERVAL rule part contains a positive integer representing how
2450    often the recurrence rule repeats. The default value is "1", meaning
2451    every second for a SECONDLY rule, or every minute for a MINUTELY
2452    rule, every hour for an HOURLY rule, every day for a DAILY rule,
2453    every week for a WEEKLY rule, every month for a MONTHLY rule and
2454    every year for a YEARLY rule.
2455
2456    The UNTIL rule part defines a date-time value which bounds the
2457    recurrence rule in an inclusive manner. If the value specified by
2458    UNTIL is synchronized with the specified recurrence, this date or
2459    date-time becomes the last instance of the recurrence. If specified
2460    as a date-time value, then it MUST be specified in an UTC time
2461    format. If not present, and the COUNT rule part is also not present,
2462    the RRULE is considered to repeat forever.
2463
2464    The COUNT rule part defines the number of occurrences at which to
2465    range-bound the recurrence. The "DTSTART" property value, if
2466
2467
2468
2469 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 42]</span>
2470 </pre><pre class="newpage"><a name="page-43" id="page-43" href="#page-43" class="invisible"> </a>
2471 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2472
2473
2474    specified, counts as the first occurrence.
2475
2476    The BYSECOND rule part specifies a COMMA character (US-ASCII decimal
2477    44) separated list of seconds within a minute. Valid values are 0 to
2478    59. The BYMINUTE rule part specifies a COMMA character (US-ASCII
2479    decimal 44) separated list of minutes within an hour. Valid values
2480    are 0 to 59. The BYHOUR rule part specifies a COMMA character (US-
2481    ASCII decimal 44) separated list of hours of the day. Valid values
2482    are 0 to 23.
2483
2484    The BYDAY rule part specifies a COMMA character (US-ASCII decimal 44)
2485    separated list of days of the week; MO indicates Monday; TU indicates
2486    Tuesday; WE indicates Wednesday; TH indicates Thursday; FR indicates
2487    Friday; SA indicates Saturday; SU indicates Sunday.
2488
2489    Each BYDAY value can also be preceded by a positive (+n) or negative
2490    (-n) integer. If present, this indicates the nth occurrence of the
2491    specific day within the MONTHLY or YEARLY RRULE. For example, within
2492    a MONTHLY rule, +1MO (or simply 1MO) represents the first Monday
2493    within the month, whereas -1MO represents the last Monday of the
2494    month. If an integer modifier is not present, it means all days of
2495    this type within the specified frequency. For example, within a
2496    MONTHLY rule, MO represents all Mondays within the month.
2497
2498    The BYMONTHDAY rule part specifies a COMMA character (ASCII decimal
2499    44) separated list of days of the month. Valid values are 1 to 31 or
2500    -31 to -1. For example, -10 represents the tenth to the last day of
2501    the month.
2502
2503    The BYYEARDAY rule part specifies a COMMA character (US-ASCII decimal
2504    44) separated list of days of the year. Valid values are 1 to 366 or
2505    -366 to -1. For example, -1 represents the last day of the year
2506    (December 31st) and -306 represents the 306th to the last day of the
2507    year (March 1st).
2508
2509    The BYWEEKNO rule part specifies a COMMA character (US-ASCII decimal
2510    44) separated list of ordinals specifying weeks of the year. Valid
2511    values are 1 to 53 or -53 to -1. This corresponds to weeks according
2512    to week numbering as defined in [ISO 8601]. A week is defined as a
2513    seven day period, starting on the day of the week defined to be the
2514    week start (see WKST). Week number one of the calendar year is the
2515    first week which contains at least four (4) days in that calendar
2516    year. This rule part is only valid for YEARLY rules. For example, 3
2517    represents the third week of the year.
2518
2519         Note: Assuming a Monday week start, week 53 can only occur when
2520         Thursday is January 1 or if it is a leap year and Wednesday is
2521         January 1.
2522
2523
2524
2525 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 43]</span>
2526 </pre><pre class="newpage"><a name="page-44" id="page-44" href="#page-44" class="invisible"> </a>
2527 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2528
2529
2530    The BYMONTH rule part specifies a COMMA character (US-ASCII decimal
2531    44) separated list of months of the year. Valid values are 1 to 12.
2532
2533    The WKST rule part specifies the day on which the workweek starts.
2534    Valid values are MO, TU, WE, TH, FR, SA and SU. This is significant
2535    when a WEEKLY RRULE has an interval greater than 1, and a BYDAY rule
2536    part is specified. This is also significant when in a YEARLY RRULE
2537    when a BYWEEKNO rule part is specified. The default value is MO.
2538
2539    The BYSETPOS rule part specifies a COMMA character (US-ASCII decimal
2540    44) separated list of values which corresponds to the nth occurrence
2541    within the set of events specified by the rule. Valid values are 1 to
2542    366 or -366 to -1. It MUST only be used in conjunction with another
2543    BYxxx rule part. For example "the last work day of the month" could
2544    be represented as:
2545
2546      RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-1
2547
2548    Each BYSETPOS value can include a positive (+n) or negative (-n)
2549    integer. If present, this indicates the nth occurrence of the
2550    specific occurrence within the set of events specified by the rule.
2551
2552    If BYxxx rule part values are found which are beyond the available
2553    scope (ie, BYMONTHDAY=30 in February), they are simply ignored.
2554
2555    Information, not contained in the rule, necessary to determine the
2556    various recurrence instance start time and dates are derived from the
2557    Start Time (DTSTART) entry attribute. For example,
2558    "FREQ=YEARLY;BYMONTH=1" doesn't specify a specific day within the
2559    month or a time. This information would be the same as what is
2560    specified for DTSTART.
2561
2562    BYxxx rule parts modify the recurrence in some manner. BYxxx rule
2563    parts for a period of time which is the same or greater than the
2564    frequency generally reduce or limit the number of occurrences of the
2565    recurrence generated. For example, "FREQ=DAILY;BYMONTH=1" reduces the
2566    number of recurrence instances from all days (if BYMONTH tag is not
2567    present) to all days in January. BYxxx rule parts for a period of
2568    time less than the frequency generally increase or expand the number
2569    of occurrences of the recurrence. For example,
2570    "FREQ=YEARLY;BYMONTH=1,2" increases the number of days within the
2571    yearly recurrence set from 1 (if BYMONTH tag is not present) to 2.
2572
2573    If multiple BYxxx rule parts are specified, then after evaluating the
2574    specified FREQ and INTERVAL rule parts, the BYxxx rule parts are
2575    applied to the current set of evaluated occurrences in the following
2576    order: BYMONTH, BYWEEKNO, BYYEARDAY, BYMONTHDAY, BYDAY, BYHOUR,
2577    BYMINUTE, BYSECOND and BYSETPOS; then COUNT and UNTIL are evaluated.
2578
2579
2580
2581 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 44]</span>
2582 </pre><pre class="newpage"><a name="page-45" id="page-45" href="#page-45" class="invisible"> </a>
2583 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2584
2585
2586    Here is an example of evaluating multiple BYxxx rule parts.
2587
2588      DTSTART;TZID=US-Eastern:19970105T083000
2589      RRULE:FREQ=YEARLY;INTERVAL=2;BYMONTH=1;BYDAY=SU;BYHOUR=8,9;
2590       BYMINUTE=30
2591
2592    First, the "INTERVAL=2" would be applied to "FREQ=YEARLY" to arrive
2593    at "every other year". Then, "BYMONTH=1" would be applied to arrive
2594    at "every January, every other year". Then, "BYDAY=SU" would be
2595    applied to arrive at "every Sunday in January, every other year".
2596    Then, "BYHOUR=8,9" would be applied to arrive at "every Sunday in
2597    January at 8 AM and 9 AM, every other year". Then, "BYMINUTE=30"
2598    would be applied to arrive at "every Sunday in January at 8:30 AM and
2599    9:30 AM, every other year". Then, lacking information from RRULE, the
2600    second is derived from DTSTART, to end up in "every Sunday in January
2601    at 8:30:00 AM and 9:30:00 AM, every other year". Similarly, if the
2602    BYMINUTE, BYHOUR, BYDAY, BYMONTHDAY or BYMONTH rule part were
2603    missing, the appropriate minute, hour, day or month would have been
2604    retrieved from the "DTSTART" property.
2605
2606    No additional content value encoding (i.e., BACKSLASH character
2607    encoding) is defined for this value type.
2608
2609    Example: The following is a rule which specifies 10 meetings which
2610    occur every other day:
2611
2612      FREQ=DAILY;COUNT=10;INTERVAL=2
2613
2614    There are other examples specified in the "RRULE" specification.
2615
2616 <span class="h4"><h4><a name="section-4.3.11">4.3.11</a> Text</h4></span>
2617
2618    Value Name: TEXT
2619
2620    Purpose This value type is used to identify values that contain human
2621    readable text.
2622
2623    Formal Definition: The character sets supported by this revision of
2624    iCalendar are UTF-8 and US ASCII thereof. The applicability to other
2625    character sets is for future work. The value type is defined by the
2626    following notation.
2627
2628      text       = *(TSAFE-CHAR / ":" / DQUOTE / ESCAPED-CHAR)
2629      ; Folded according to description above
2630
2631      ESCAPED-CHAR = "\\" / "\;" / "\," / "\N" / "\n")
2632         ; \\ encodes \, \N or \n encodes newline
2633         ; \; encodes ;, \, encodes ,
2634
2635
2636
2637 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 45]</span>
2638 </pre><pre class="newpage"><a name="page-46" id="page-46" href="#page-46" class="invisible"> </a>
2639 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2640
2641
2642      TSAFE-CHAR = %x20-21 / %x23-2B / %x2D-39 / %x3C-5B
2643                   %x5D-7E / NON-US-ASCII
2644         ; Any character except CTLs not needed by the current
2645         ; character set, DQUOTE, ";", ":", "\", ","
2646
2647      Note: Certain other character sets may require modification of the
2648      above definitions, but this is beyond the scope of this document.
2649
2650    Description: If the property permits, multiple "text" values are
2651    specified by a COMMA character (US-ASCII decimal 44) separated list
2652    of values.
2653
2654    The language in which the text is represented can be controlled by
2655    the "LANGUAGE" property parameter.
2656
2657    An intentional formatted text line break MUST only be included in a
2658    "TEXT" property value by representing the line break with the
2659    character sequence of BACKSLASH (US-ASCII decimal 92), followed by a
2660    LATIN SMALL LETTER N (US-ASCII decimal 110) or a LATIN CAPITAL LETTER
2661    N (US-ASCII decimal 78), that is "\n" or "\N".
2662
2663    The "TEXT" property values may also contain special characters that
2664    are used to signify delimiters, such as a COMMA character for lists
2665    of values or a SEMICOLON character for structured values. In order to
2666    support the inclusion of these special characters in "TEXT" property
2667    values, they MUST be escaped with a BACKSLASH character. A BACKSLASH
2668    character (US-ASCII decimal 92) in a "TEXT" property value MUST be
2669    escaped with another BACKSLASH character. A COMMA character in a
2670    "TEXT" property value MUST be escaped with a BACKSLASH character
2671    (US-ASCII decimal 92). A SEMICOLON character in a "TEXT" property
2672    value MUST be escaped with a BACKSLASH character (US-ASCII decimal
2673    92).  However, a COLON character in a "TEXT" property value SHALL NOT
2674    be escaped with a BACKSLASH character.Example: A multiple line value
2675    of:
2676
2677      Project XYZ Final Review
2678      Conference Room - 3B
2679      Come Prepared.
2680
2681    would be represented as:
2682
2683      Project XYZ Final Review\nConference Room - 3B\nCome Prepared.
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 46]</span>
2694 </pre><pre class="newpage"><a name="page-47" id="page-47" href="#page-47" class="invisible"> </a>
2695 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2696
2697
2698 <span class="h4"><h4><a name="section-4.3.12">4.3.12</a> Time</h4></span>
2699
2700    Value Name: TIME
2701
2702    Purpose: This value type is used to identify values that contain a
2703    time of day.
2704
2705    Formal Definition: The data type is defined by the following
2706    notation:
2707
2708      time               = time-hour time-minute time-second [<a href="#ref-time-utc">time-utc</a>]
2709
2710      time-hour          = 2DIGIT        ;00-23
2711      time-minute        = 2DIGIT        ;00-59
2712      time-second        = 2DIGIT        ;00-60
2713      ;The "60" value is used to account for "leap" seconds.
2714
2715      time-utc   = "Z"
2716
2717    Description: If the property permits, multiple "time" values are
2718    specified by a COMMA character (US-ASCII decimal 44) separated list
2719    of values. No additional content value encoding (i.e., BACKSLASH
2720    character encoding) is defined for this value type.
2721
2722    The "TIME" data type is used to identify values that contain a time
2723    of day. The format is based on the [ISO 8601] complete
2724    representation, basic format for a time of day. The text format
2725    consists of a two-digit 24-hour of the day (i.e., values 0-23), two-
2726    digit minute in the hour (i.e., values 0-59), and two-digit seconds
2727    in the minute (i.e., values 0-60). The seconds value of 60 MUST only
2728    to be used to account for "leap" seconds. Fractions of a second are
2729    not supported by this format.
2730
2731    In parallel to the "DATE-TIME" definition above, the "TIME" data type
2732    expresses time values in three forms:
2733
2734    The form of time with UTC offset MUST NOT be used. For example, the
2735    following is NOT VALID for a time value:
2736
2737      230000-0800        ;Invalid time format
2738
2739    FORM #1 LOCAL TIME
2740
2741    The local time form is simply a time value that does not contain the
2742    UTC designator nor does it reference a time zone. For example, 11:00
2743    PM:
2744
2745      230000
2746
2747
2748
2749 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 47]</span>
2750 </pre><pre class="newpage"><a name="page-48" id="page-48" href="#page-48" class="invisible"> </a>
2751 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2752
2753
2754    Time values of this type are said to be "floating" and are not bound
2755    to any time zone in particular. They are used to represent the same
2756    hour, minute, and second value regardless of which time zone is
2757    currently being observed. For example, an event can be defined that
2758    indicates that an individual will be busy from 11:00 AM to 1:00 PM
2759    every day, no matter which time zone the person is in. In these
2760    cases, a local time can be specified. The recipient of an iCalendar
2761    object with a property value consisting of a local time, without any
2762    relative time zone information, SHOULD interpret the value as being
2763    fixed to whatever time zone the ATTENDEE is in at any given moment.
2764    This means that two ATTENDEEs may participate in the same event at
2765    different UTC times; floating time SHOULD only be used where that is
2766    reasonable behavior.
2767
2768    In most cases, a fixed time is desired. To properly communicate a
2769    fixed time in a property value, either UTC time or local time with
2770    time zone reference MUST be specified.
2771
2772    The use of local time in a TIME value without the TZID property
2773    parameter is to be interpreted as a local time value, regardless of
2774    the existence of "VTIMEZONE" calendar components in the iCalendar
2775    object.
2776
2777    FORM #2: UTC TIME
2778
2779    UTC time, or absolute time, is identified by a LATIN CAPITAL LETTER Z
2780    suffix character (US-ASCII decimal 90), the UTC designator, appended
2781    to the time value. For example, the following represents 07:00 AM
2782    UTC:
2783
2784      070000Z
2785
2786    The TZID property parameter MUST NOT be applied to TIME properties
2787    whose time values are specified in UTC.
2788
2789    FORM #3: LOCAL TIME AND TIME ZONE REFERENCE
2790
2791    The local time with reference to time zone information form is
2792    identified by the use the TZID property parameter to reference the
2793    appropriate time zone definition. TZID is discussed in detail in the
2794    section on Time Zone.
2795
2796    Example: The following represents 8:30 AM in New York in Winter, five
2797    hours behind UTC, in each of the three formats using the "X-
2798    TIMEOFDAY" non-standard property:
2799
2800
2801
2802
2803
2804
2805 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 48]</span>
2806 </pre><pre class="newpage"><a name="page-49" id="page-49" href="#page-49" class="invisible"> </a>
2807 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2808
2809
2810      X-TIMEOFDAY:083000
2811
2812      X-TIMEOFDAY:133000Z
2813
2814      X-TIMEOFDAY;TZID=US-Eastern:083000
2815
2816 <span class="h4"><h4><a name="section-4.3.13">4.3.13</a> URI</h4></span>
2817
2818    Value Name: URI
2819
2820    Purpose: This value type is used to identify values that contain a
2821    uniform resource identifier (URI) type of reference to the property
2822    value.
2823
2824    Formal Definition: The data type is defined by the following
2825    notation:
2826
2827      uri        = &lt;As defined by any IETF RFC&gt;
2828
2829    Description: This data type might be used to reference binary
2830    information, for values that are large, or otherwise undesirable to
2831    include directly in the iCalendar object.
2832
2833    The URI value formats in <a href="http://tools.ietf.org/html/rfc1738">RFC 1738</a>, <a href="http://tools.ietf.org/html/rfc2111">RFC 2111</a> and any other IETF
2834    registered value format can be specified.
2835
2836    Any IANA registered URI format can be used. These include, but are
2837    not limited to, those defined in <a href="http://tools.ietf.org/html/rfc1738">RFC 1738</a> and <a href="http://tools.ietf.org/html/rfc2111">RFC 2111</a>.
2838
2839    When a property parameter value is a URI value type, the URI MUST be
2840    specified as a quoted-string value.
2841
2842    No additional content value encoding (i.e., BACKSLASH character
2843    encoding) is defined for this value type.
2844
2845    Example: The following is a URI for a network file:
2846
2847      <a href="http://host1.com/my-report.txt">http://host1.com/my-report.txt</a>
2848
2849 <span class="h4"><h4><a name="section-4.3.14">4.3.14</a> UTC Offset</h4></span>
2850
2851    Value Name: UTC-OFFSET
2852
2853    Purpose: This value type is used to identify properties that contain
2854    an offset from UTC to local time.
2855
2856    Formal Definition: The data type is defined by the following
2857    notation:
2858
2859
2860
2861 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 49]</span>
2862 </pre><pre class="newpage"><a name="page-50" id="page-50" href="#page-50" class="invisible"> </a>
2863 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2864
2865
2866      utc-offset = time-numzone  ;As defined above in time data type
2867
2868      time-numzone       = ("+" / "-") time-hour time-minute [time-
2869      second]
2870
2871    Description: The PLUS SIGN character MUST be specified for positive
2872    UTC offsets (i.e., ahead of UTC). The value of "-0000" and "-000000"
2873    are not allowed. The time-second, if present, may not be 60; if
2874    absent, it defaults to zero.
2875
2876    No additional content value encoding (i.e., BACKSLASH character
2877    encoding) is defined for this value type.
2878
2879    Example: The following UTC offsets are given for standard time for
2880    New York (five hours behind UTC) and Geneva (one hour ahead of UTC):
2881
2882      -0500
2883
2884      +0100
2885
2886 <span class="h3"><h3><a name="section-4.4">4.4</a> iCalendar Object</h3></span>
2887
2888    The Calendaring and Scheduling Core Object is a collection of
2889    calendaring and scheduling information. Typically, this information
2890    will consist of a single iCalendar object. However, multiple
2891    iCalendar objects can be sequentially grouped together. The first
2892    line and last line of the iCalendar object MUST contain a pair of
2893    iCalendar object delimiter strings. The syntax for an iCalendar
2894    object is as follows:
2895
2896      icalobject = 1*("BEGIN" ":" "VCALENDAR" CRLF
2897                   icalbody
2898                   "END" ":" "VCALENDAR" CRLF)
2899
2900    The following is a simple example of an iCalendar object:
2901
2902      BEGIN:VCALENDAR
2903      VERSION:2.0
2904      PRODID:-//hacksw/handcal//NONSGML v1.0//EN
2905      BEGIN:VEVENT
2906      DTSTART:19970714T170000Z
2907      DTEND:19970715T035959Z
2908      SUMMARY:Bastille Day Party
2909      END:VEVENT
2910      END:VCALENDAR
2911
2912
2913
2914
2915
2916
2917 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 50]</span>
2918 </pre><pre class="newpage"><a name="page-51" id="page-51" href="#page-51" class="invisible"> </a>
2919 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2920
2921
2922 <span class="h3"><h3><a name="section-4.5">4.5</a> Property</h3></span>
2923
2924    A property is the definition of an individual attribute describing a
2925    calendar or a calendar component. A property takes the form defined
2926    by the "contentline" notation defined in <a href="#section-4.1.1">section 4.1.1</a>.
2927
2928    The following is an example of a property:
2929
2930      DTSTART:19960415T133000Z
2931
2932    This memo imposes no ordering of properties within an iCalendar
2933    object.
2934
2935    Property names, parameter names and enumerated parameter values are
2936    case insensitive. For example, the property name "DUE" is the same as
2937    "due" and "Due", DTSTART;TZID=US-Eastern:19980714T120000 is the same
2938    as DtStart;TzID=US-Eastern:19980714T120000.
2939
2940 <span class="h3"><h3><a name="section-4.6">4.6</a> Calendar Components</h3></span>
2941
2942    The body of the iCalendar object consists of a sequence of calendar
2943    properties and one or more calendar components. The calendar
2944    properties are attributes that apply to the calendar as a whole. The
2945    calendar components are collections of properties that express a
2946    particular calendar semantic. For example, the calendar component can
2947    specify an event, a to-do, a journal entry, time zone information, or
2948    free/busy time information, or an alarm.
2949
2950    The body of the iCalendar object is defined by the following
2951    notation:
2952
2953      icalbody   = calprops component
2954
2955      calprops   = 2*(
2956
2957                 ; 'prodid' and 'version' are both REQUIRED,
2958                 ; but MUST NOT occur more than once
2959
2960                 prodid /version /
2961
2962                 ; 'calscale' and 'method' are optional,
2963                 ; but MUST NOT occur more than once
2964
2965                 calscale        /
2966                 method          /
2967
2968                 x-prop
2969
2970
2971
2972
2973 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 51]</span>
2974 </pre><pre class="newpage"><a name="page-52" id="page-52" href="#page-52" class="invisible"> </a>
2975 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
2976
2977
2978                 )
2979
2980      component  = 1*(eventc / todoc / journalc / freebusyc /
2981                 / timezonec / iana-comp / x-comp)
2982
2983      iana-comp  = "BEGIN" ":" iana-token CRLF
2984
2985                   1*contentline
2986
2987                   "END" ":" iana-token CRLF
2988
2989      x-comp     = "BEGIN" ":" x-name CRLF
2990
2991                   1*contentline
2992
2993                   "END" ":" x-name CRLF
2994
2995    An iCalendar object MUST include the "PRODID" and "VERSION" calendar
2996    properties. In addition, it MUST include at least one calendar
2997    component. Special forms of iCalendar objects are possible to publish
2998    just busy time (i.e., only a "VFREEBUSY" calendar component) or time
2999    zone (i.e., only a "VTIMEZONE" calendar component) information. In
3000    addition, a complex iCalendar object is possible that is used to
3001    capture a complete snapshot of the contents of a calendar (e.g.,
3002    composite of many different calendar components). More commonly, an
3003    iCalendar object will consist of just a single "VEVENT", "VTODO" or
3004    "VJOURNAL" calendar component.
3005
3006 <span class="h4"><h4><a name="section-4.6.1">4.6.1</a> Event Component</h4></span>
3007
3008    Component Name: "VEVENT"
3009
3010    Purpose: Provide a grouping of component properties that describe an
3011    event.
3012
3013    Format Definition: A "VEVENT" calendar component is defined by the
3014    following notation:
3015
3016      eventc     = "BEGIN" ":" "VEVENT" CRLF
3017                   eventprop *alarmc
3018                   "END" ":" "VEVENT" CRLF
3019
3020      eventprop  = *(
3021
3022                 ; the following are optional,
3023                 ; but MUST NOT occur more than once
3024
3025                 class / created / description / dtstart / geo /
3026
3027
3028
3029 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 52]</span>
3030 </pre><pre class="newpage"><a name="page-53" id="page-53" href="#page-53" class="invisible"> </a>
3031 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3032
3033
3034                 last-mod / location / organizer / priority /
3035                 dtstamp / seq / status / summary / transp /
3036                 uid / url / recurid /
3037
3038                 ; either 'dtend' or 'duration' may appear in
3039                 ; a 'eventprop', but 'dtend' and 'duration'
3040                 ; MUST NOT occur in the same 'eventprop'
3041
3042                 dtend / duration /
3043
3044                 ; the following are optional,
3045                 ; and MAY occur more than once
3046
3047                 attach / attendee / categories / comment /
3048                 contact / exdate / exrule / rstatus / related /
3049                 resources / rdate / rrule / x-prop
3050
3051                 )
3052
3053    Description: A "VEVENT" calendar component is a grouping of component
3054    properties, and possibly including "VALARM" calendar components, that
3055    represents a scheduled amount of time on a calendar. For example, it
3056    can be an activity; such as a one-hour long, department meeting from
3057    8:00 AM to 9:00 AM, tomorrow. Generally, an event will take up time
3058    on an individual calendar. Hence, the event will appear as an opaque
3059    interval in a search for busy time. Alternately, the event can have
3060    its Time Transparency set to "TRANSPARENT" in order to prevent
3061    blocking of the event in searches for busy time.
3062
3063    The "VEVENT" is also the calendar component used to specify an
3064    anniversary or daily reminder within a calendar. These events have a
3065    DATE value type for the "DTSTART" property instead of the default
3066    data type of DATE-TIME. If such a "VEVENT" has a "DTEND" property, it
3067    MUST be specified as a DATE value also. The anniversary type of
3068    "VEVENT" can span more than one date (i.e, "DTEND" property value is
3069    set to a calendar date after the "DTSTART" property value).
3070
3071    The "DTSTART" property for a "VEVENT" specifies the inclusive start
3072    of the event. For recurring events, it also specifies the very first
3073    instance in the recurrence set. The "DTEND" property for a "VEVENT"
3074    calendar component specifies the non-inclusive end of the event. For
3075    cases where a "VEVENT" calendar component specifies a "DTSTART"
3076    property with a DATE data type but no "DTEND" property, the events
3077    non-inclusive end is the end of the calendar date specified by the
3078    "DTSTART" property. For cases where a "VEVENT" calendar component
3079    specifies a "DTSTART" property with a DATE-TIME data type but no
3080    "DTEND" property, the event ends on the same calendar date and time
3081    of day specified by the "DTSTART" property.
3082
3083
3084
3085 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 53]</span>
3086 </pre><pre class="newpage"><a name="page-54" id="page-54" href="#page-54" class="invisible"> </a>
3087 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3088
3089
3090    The "VEVENT" calendar component cannot be nested within another
3091    calendar component. However, "VEVENT" calendar components can be
3092    related to each other or to a "VTODO" or to a "VJOURNAL" calendar
3093    component with the "RELATED-TO" property.
3094
3095    Example: The following is an example of the "VEVENT" calendar
3096    component used to represent a meeting that will also be opaque to
3097    searches for busy time:
3098
3099      BEGIN:VEVENT
3100      UID:19970901T130000Z-123401@host.com
3101      DTSTAMP:19970901T1300Z
3102      DTSTART:19970903T163000Z
3103      DTEND:19970903T190000Z
3104      SUMMARY:Annual Employee Review
3105      CLASS:PRIVATE
3106      CATEGORIES:BUSINESS,HUMAN RESOURCES
3107      END:VEVENT
3108
3109    The following is an example of the "VEVENT" calendar component used
3110    to represent a reminder that will not be opaque, but rather
3111    transparent, to searches for busy time:
3112
3113      BEGIN:VEVENT
3114      UID:19970901T130000Z-123402@host.com
3115      DTSTAMP:19970901T1300Z
3116      DTSTART:19970401T163000Z
3117      DTEND:19970402T010000Z
3118      SUMMARY:Laurel is in sensitivity awareness class.
3119      CLASS:PUBLIC
3120      CATEGORIES:BUSINESS,HUMAN RESOURCES
3121      TRANSP:TRANSPARENT
3122      END:VEVENT
3123
3124    The following is an example of the "VEVENT" calendar component used
3125    to represent an anniversary that will occur annually. Since it takes
3126    up no time, it will not appear as opaque in a search for busy time;
3127    no matter what the value of the "TRANSP" property indicates:
3128
3129      BEGIN:VEVENT
3130      UID:19970901T130000Z-123403@host.com
3131      DTSTAMP:19970901T1300Z
3132      DTSTART:19971102
3133      SUMMARY:Our Blissful Anniversary
3134      CLASS:CONFIDENTIAL
3135      CATEGORIES:ANNIVERSARY,PERSONAL,SPECIAL OCCASION
3136      RRULE:FREQ=YEARLY
3137      END:VEVENT
3138
3139
3140
3141 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 54]</span>
3142 </pre><pre class="newpage"><a name="page-55" id="page-55" href="#page-55" class="invisible"> </a>
3143 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3144
3145
3146 <span class="h4"><h4><a name="section-4.6.2">4.6.2</a> To-do Component</h4></span>
3147
3148    Component Name: VTODO
3149
3150    Purpose: Provide a grouping of calendar properties that describe a
3151    to-do.
3152
3153    Formal Definition: A "VTODO" calendar component is defined by the
3154    following notation:
3155
3156      todoc      = "BEGIN" ":" "VTODO" CRLF
3157                   todoprop *alarmc
3158                   "END" ":" "VTODO" CRLF
3159
3160      todoprop   = *(
3161
3162                 ; the following are optional,
3163                 ; but MUST NOT occur more than once
3164
3165                 class / completed / created / description / dtstamp /
3166                 dtstart / geo / last-mod / location / organizer /
3167                 percent / priority / recurid / seq / status /
3168                 summary / uid / url /
3169
3170                 ; either 'due' or 'duration' may appear in
3171                 ; a 'todoprop', but 'due' and 'duration'
3172                 ; MUST NOT occur in the same 'todoprop'
3173
3174                 due / duration /
3175
3176                 ; the following are optional,
3177                 ; and MAY occur more than once
3178                 attach / attendee / categories / comment / contact /
3179                 exdate / exrule / rstatus / related / resources /
3180                 rdate / rrule / x-prop
3181
3182                 )
3183
3184    Description: A "VTODO" calendar component is a grouping of component
3185    properties and possibly "VALARM" calendar components that represent
3186    an action-item or assignment. For example, it can be used to
3187    represent an item of work assigned to an individual; such as "turn in
3188    travel expense today".
3189
3190    The "VTODO" calendar component cannot be nested within another
3191    calendar component. However, "VTODO" calendar components can be
3192    related to each other or to a "VTODO" or to a "VJOURNAL" calendar
3193    component with the "RELATED-TO" property.
3194
3195
3196
3197 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 55]</span>
3198 </pre><pre class="newpage"><a name="page-56" id="page-56" href="#page-56" class="invisible"> </a>
3199 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3200
3201
3202    A "VTODO" calendar component without the "DTSTART" and "DUE" (or
3203    "DURATION") properties specifies a to-do that will be associated with
3204    each successive calendar date, until it is completed.
3205
3206    Example: The following is an example of a "VTODO" calendar component:
3207
3208      BEGIN:VTODO
3209      UID:19970901T130000Z-123404@host.com
3210      DTSTAMP:19970901T1300Z
3211      DTSTART:19970415T133000Z
3212      DUE:19970416T045959Z
3213      SUMMARY:1996 Income Tax Preparation
3214      CLASS:CONFIDENTIAL
3215      CATEGORIES:FAMILY,FINANCE
3216      PRIORITY:1
3217      STATUS:NEEDS-ACTION
3218      END:VTODO
3219
3220 <span class="h4"><h4><a name="section-4.6.3">4.6.3</a> Journal Component</h4></span>
3221
3222    Component Name: VJOURNAL
3223
3224    Purpose: Provide a grouping of component properties that describe a
3225    journal entry.
3226
3227    Formal Definition: A "VJOURNAL" calendar component is defined by the
3228    following notation:
3229
3230      journalc   = "BEGIN" ":" "VJOURNAL" CRLF
3231                   jourprop
3232                   "END" ":" "VJOURNAL" CRLF
3233
3234      jourprop   = *(
3235
3236                 ; the following are optional,
3237                 ; but MUST NOT occur more than once
3238
3239                 class / created / description / dtstart / dtstamp /
3240                 last-mod / organizer / recurid / seq / status /
3241                 summary / uid / url /
3242
3243                 ; the following are optional,
3244                 ; and MAY occur more than once
3245
3246                 attach / attendee / categories / comment /
3247                 contact / exdate / exrule / related / rdate /
3248                 rrule / rstatus / x-prop
3249
3250
3251
3252
3253 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 56]</span>
3254 </pre><pre class="newpage"><a name="page-57" id="page-57" href="#page-57" class="invisible"> </a>
3255 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3256
3257
3258                 )
3259
3260    Description: A "VJOURNAL" calendar component is a grouping of
3261    component properties that represent one or more descriptive text
3262    notes associated with a particular calendar date. The "DTSTART"
3263    property is used to specify the calendar date that the journal entry
3264    is associated with. Generally, it will have a DATE value data type,
3265    but it can also be used to specify a DATE-TIME value data type.
3266    Examples of a journal entry include a daily record of a legislative
3267    body or a journal entry of individual telephone contacts for the day
3268    or an ordered list of accomplishments for the day. The "VJOURNAL"
3269    calendar component can also be used to associate a document with a
3270    calendar date.
3271
3272    The "VJOURNAL" calendar component does not take up time on a
3273    calendar. Hence, it does not play a role in free or busy time
3274    searches - - it is as though it has a time transparency value of
3275    TRANSPARENT. It is transparent to any such searches.
3276
3277    The "VJOURNAL" calendar component cannot be nested within another
3278    calendar component. However, "VJOURNAL" calendar components can be
3279    related to each other or to a "VEVENT" or to a "VTODO" calendar
3280    component, with the "RELATED-TO" property.
3281
3282    Example: The following is an example of the "VJOURNAL" calendar
3283    component:
3284
3285      BEGIN:VJOURNAL
3286      UID:19970901T130000Z-123405@host.com
3287      DTSTAMP:19970901T1300Z
3288      DTSTART;VALUE=DATE:19970317
3289      SUMMARY:Staff meeting minutes
3290      DESCRIPTION:1. Staff meeting: Participants include Joe\, Lisa
3291        and Bob. Aurora project plans were reviewed. There is currently
3292        no budget reserves for this project. Lisa will escalate to
3293        management. Next meeting on Tuesday.\n
3294        2. Telephone Conference: ABC Corp. sales representative called
3295        to discuss new printer. Promised to get us a demo by Friday.\n
3296        3. Henry Miller (Handsoff Insurance): Car was totaled by tree.
3297        Is looking into a loaner car. 654-2323 (tel).
3298      END:VJOURNAL
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 57]</span>
3310 </pre><pre class="newpage"><a name="page-58" id="page-58" href="#page-58" class="invisible"> </a>
3311 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3312
3313
3314 <span class="h4"><h4><a name="section-4.6.4">4.6.4</a> Free/Busy Component</h4></span>
3315
3316    Component Name: VFREEBUSY
3317
3318    Purpose: Provide a grouping of component properties that describe
3319    either a request for free/busy time, describe a response to a request
3320    for free/busy time or describe a published set of busy time.
3321
3322    Formal Definition: A "VFREEBUSY" calendar component is defined by the
3323    following notation:
3324
3325      freebusyc  = "BEGIN" ":" "VFREEBUSY" CRLF
3326                   fbprop
3327                   "END" ":" "VFREEBUSY" CRLF
3328
3329      fbprop     = *(
3330
3331                 ; the following are optional,
3332                 ; but MUST NOT occur more than once
3333
3334                 contact / dtstart / dtend / duration / dtstamp /
3335                 organizer / uid / url /
3336
3337                 ; the following are optional,
3338                 ; and MAY occur more than once
3339
3340                 attendee / comment / freebusy / rstatus / x-prop
3341
3342                 )
3343
3344    Description: A "VFREEBUSY" calendar component is a grouping of
3345    component properties that represents either a request for, a reply to
3346    a request for free or busy time information or a published set of
3347    busy time information.
3348
3349    When used to request free/busy time information, the "ATTENDEE"
3350    property specifies the calendar users whose free/busy time is being
3351    requested; the "ORGANIZER" property specifies the calendar user who
3352    is requesting the free/busy time; the "DTSTART" and "DTEND"
3353    properties specify the window of time for which the free/busy time is
3354    being requested; the "UID" and "DTSTAMP" properties are specified to
3355    assist in proper sequencing of multiple free/busy time requests.
3356
3357    When used to reply to a request for free/busy time, the "ATTENDEE"
3358    property specifies the calendar user responding to the free/busy time
3359    request; the "ORGANIZER" property specifies the calendar user that
3360    originally requested the free/busy time; the "FREEBUSY" property
3361    specifies the free/busy time information (if it exists); and the
3362
3363
3364
3365 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 58]</span>
3366 </pre><pre class="newpage"><a name="page-59" id="page-59" href="#page-59" class="invisible"> </a>
3367 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3368
3369
3370    "UID" and "DTSTAMP" properties are specified to assist in proper
3371    sequencing of multiple free/busy time replies.
3372
3373    When used to publish busy time, the "ORGANIZER" property specifies
3374    the calendar user associated with the published busy time; the
3375    "DTSTART" and "DTEND" properties specify an inclusive time window
3376    that surrounds the busy time information; the "FREEBUSY" property
3377    specifies the published busy time information; and the "DTSTAMP"
3378    property specifies the date/time that iCalendar object was created.
3379
3380    The "VFREEBUSY" calendar component cannot be nested within another
3381    calendar component. Multiple "VFREEBUSY" calendar components can be
3382    specified within an iCalendar object. This permits the grouping of
3383    Free/Busy information into logical collections, such as monthly
3384    groups of busy time information.
3385
3386    The "VFREEBUSY" calendar component is intended for use in iCalendar
3387    object methods involving requests for free time, requests for busy
3388    time, requests for both free and busy, and the associated replies.
3389
3390    Free/Busy information is represented with the "FREEBUSY" property.
3391    This property provides a terse representation of time periods. One or
3392    more "FREEBUSY" properties can be specified in the "VFREEBUSY"
3393    calendar component.
3394
3395    When present in a "VFREEBUSY" calendar component, the "DTSTART" and
3396    "DTEND" properties SHOULD be specified prior to any "FREEBUSY"
3397    properties. In a free time request, these properties can be used in
3398    combination with the "DURATION" property to represent a request for a
3399    duration of free time within a specified window of time.
3400
3401    The recurrence properties ("RRULE", "EXRULE", "RDATE", "EXDATE") are
3402    not permitted within a "VFREEBUSY" calendar component. Any recurring
3403    events are resolved into their individual busy time periods using the
3404    "FREEBUSY" property.
3405
3406    Example: The following is an example of a "VFREEBUSY" calendar
3407    component used to request free or busy time information:
3408
3409      BEGIN:VFREEBUSY
3410      ORGANIZER:MAILTO:jane_doe@host1.com
3411      ATTENDEE:MAILTO:john_public@host2.com
3412      DTSTART:19971015T050000Z
3413      DTEND:19971016T050000Z
3414      DTSTAMP:19970901T083000Z
3415      END:VFREEBUSY
3416
3417
3418
3419
3420
3421 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 59]</span>
3422 </pre><pre class="newpage"><a name="page-60" id="page-60" href="#page-60" class="invisible"> </a>
3423 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3424
3425
3426    The following is an example of a "VFREEBUSY" calendar component used
3427    to reply to the request with busy time information:
3428
3429      BEGIN:VFREEBUSY
3430      ORGANIZER:MAILTO:jane_doe@host1.com
3431      ATTENDEE:MAILTO:john_public@host2.com
3432      DTSTAMP:19970901T100000Z
3433      FREEBUSY;VALUE=PERIOD:19971015T050000Z/PT8H30M,
3434       19971015T160000Z/PT5H30M,19971015T223000Z/PT6H30M
3435      URL:http://host2.com/pub/busy/jpublic-01.ifb
3436      COMMENT:This iCalendar file contains busy time information for
3437        the next three months.
3438      END:VFREEBUSY
3439
3440    The following is an example of a "VFREEBUSY" calendar component used
3441    to publish busy time information.
3442
3443      BEGIN:VFREEBUSY
3444      ORGANIZER:jsmith@host.com
3445      DTSTART:19980313T141711Z
3446      DTEND:19980410T141711Z
3447      FREEBUSY:19980314T233000Z/19980315T003000Z
3448      FREEBUSY:19980316T153000Z/19980316T163000Z
3449      FREEBUSY:19980318T030000Z/19980318T040000Z
3450      URL:http://www.host.com/calendar/busytime/jsmith.ifb
3451      END:VFREEBUSY
3452
3453 <span class="h4"><h4><a name="section-4.6.5">4.6.5</a> Time Zone Component</h4></span>
3454
3455    Component Name: VTIMEZONE
3456
3457    Purpose: Provide a grouping of component properties that defines a
3458    time zone.
3459
3460    Formal Definition: A "VTIMEZONE" calendar component is defined by the
3461    following notation:
3462
3463      timezonec  = "BEGIN" ":" "VTIMEZONE" CRLF
3464
3465                   2*(
3466
3467                   ; 'tzid' is required, but MUST NOT occur more
3468                   ; than once
3469
3470                 tzid /
3471
3472                   ; 'last-mod' and 'tzurl' are optional,
3473                 but MUST NOT occur more than once
3474
3475
3476
3477 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 60]</span>
3478 </pre><pre class="newpage"><a name="page-61" id="page-61" href="#page-61" class="invisible"> </a>
3479 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3480
3481
3482                 last-mod / tzurl /
3483
3484                   ; one of 'standardc' or 'daylightc' MUST occur
3485                 ..; and each MAY occur more than once.
3486
3487                 standardc / daylightc /
3488
3489                 ; the following is optional,
3490                 ; and MAY occur more than once
3491
3492                   x-prop
3493
3494                   )
3495
3496                   "END" ":" "VTIMEZONE" CRLF
3497
3498      standardc  = "BEGIN" ":" "STANDARD" CRLF
3499
3500                   tzprop
3501
3502                   "END" ":" "STANDARD" CRLF
3503
3504      daylightc  = "BEGIN" ":" "DAYLIGHT" CRLF
3505
3506                   tzprop
3507
3508                   "END" ":" "DAYLIGHT" CRLF
3509
3510      tzprop     = 3*(
3511
3512                 ; the following are each REQUIRED,
3513                 ; but MUST NOT occur more than once
3514
3515                 dtstart / tzoffsetto / tzoffsetfrom /
3516
3517                 ; the following are optional,
3518                 ; and MAY occur more than once
3519
3520                 comment / rdate / rrule / tzname / x-prop
3521
3522                 )
3523
3524    Description: A time zone is unambiguously defined by the set of time
3525    measurement rules determined by the governing body for a given
3526    geographic area. These rules describe at a minimum the base  offset
3527    from UTC for the time zone, often referred to as the Standard Time
3528    offset. Many locations adjust their Standard Time forward or backward
3529    by one hour, in order to accommodate seasonal changes in number of
3530
3531
3532
3533 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 61]</span>
3534 </pre><pre class="newpage"><a name="page-62" id="page-62" href="#page-62" class="invisible"> </a>
3535 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3536
3537
3538    daylight hours, often referred to as Daylight  Saving Time. Some
3539    locations adjust their time by a fraction of an hour. Standard Time
3540    is also known as Winter Time. Daylight Saving Time is also known as
3541    Advanced Time, Summer Time, or Legal Time in certain countries. The
3542    following table shows the changes in time zone rules in effect for
3543    New York City starting from 1967. Each line represents a description
3544    or rule for a particular observance.
3545
3546      Effective Observance Rule
3547
3548      Date       (Date/Time)             Offset  Abbreviation
3549
3550      1967-*     last Sun in Oct, 02:00  -0500   EST
3551
3552      1967-1973  last Sun in Apr, 02:00  -0400   EDT
3553
3554      1974-1974  Jan 6,  02:00           -0400   EDT
3555
3556      1975-1975  Feb 23, 02:00           -0400   EDT
3557
3558      1976-1986  last Sun in Apr, 02:00  -0400   EDT
3559
3560      1987-*     first Sun in Apr, 02:00 -0400   EDT
3561
3562         Note: The specification of a global time zone registry is not
3563         addressed by this document and is left for future study.
3564         However, implementers may find the Olson time zone database [<a href="#ref-TZ" title="&quot;ftp://elsie.nci.nih.gov/pub/&quot;">TZ</a>]
3565         a useful reference. It is an informal, public-domain collection
3566         of time zone information, which is currently being maintained by
3567         volunteer Internet participants, and is used in several
3568         operating systems. This database contains current and historical
3569         time zone information for a wide variety of locations around the
3570         globe; it provides a time zone identifier for every unique time
3571         zone rule set in actual use since 1970, with historical data
3572         going back to the introduction of standard time.
3573
3574    Interoperability between two calendaring and scheduling applications,
3575    especially for recurring events, to-dos or journal entries, is
3576    dependent on the ability to capture and convey date and time
3577    information in an unambiguous format. The specification of current
3578    time zone information is integral to this behavior.
3579
3580    If present, the "VTIMEZONE" calendar component defines the set of
3581    Standard Time and Daylight Saving Time observances (or rules) for a
3582    particular time zone for a given interval of time. The "VTIMEZONE"
3583    calendar component cannot be nested within other calendar components.
3584    Multiple "VTIMEZONE" calendar components can exist in an iCalendar
3585    object. In this situation, each "VTIMEZONE" MUST represent a unique
3586
3587
3588
3589 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 62]</span>
3590 </pre><pre class="newpage"><a name="page-63" id="page-63" href="#page-63" class="invisible"> </a>
3591 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3592
3593
3594    time zone definition. This is necessary for some classes of events,
3595    such as airline flights, that start in one time zone and end in
3596    another.
3597
3598    The "VTIMEZONE" calendar component MUST be present if the iCalendar
3599    object contains an RRULE that generates dates on both sides of a time
3600    zone shift (e.g. both in Standard Time and Daylight Saving Time)
3601    unless the iCalendar object intends to convey a floating time (See
3602    the section "4.1.10.11 Time" for proper interpretation of floating
3603    time). It can be present if the iCalendar object does not contain
3604    such a RRULE. In addition, if a RRULE is present, there MUST be valid
3605    time zone information for all recurrence instances.
3606
3607    The "VTIMEZONE" calendar component MUST include the "TZID" property
3608    and at least one definition of a standard or daylight component. The
3609    standard or daylight component MUST include the "DTSTART",
3610    "TZOFFSETFROM" and "TZOFFSETTO" properties.
3611
3612    An individual "VTIMEZONE" calendar component MUST be specified for
3613    each unique "TZID" parameter value specified in the iCalendar object.
3614
3615    Each "VTIMEZONE" calendar component consists of a collection of one
3616    or more sub-components that describe the rule for a particular
3617    observance (either a Standard Time or a Daylight Saving Time
3618    observance). The "STANDARD" sub-component consists of a collection of
3619    properties that describe Standard Time. The "DAYLIGHT" sub-component
3620    consists of a collection of properties that describe Daylight Saving
3621    Time. In general this collection of properties consists of:
3622
3623         - the first onset date-time for the observance
3624
3625         - the last onset date-time for the observance, if a last onset
3626           is known.
3627
3628         - the offset to be applied for the observance
3629
3630         - a rule that describes the day and time when the observance
3631           takes effect
3632
3633         - an optional name for the observance
3634
3635    For a given time zone, there may be multiple unique definitions of
3636    the observances over a period of time. Each observance is described
3637    using either a "STANDARD" or "DAYLIGHT" sub-component. The collection
3638    of these sub-components is used to describe the time zone for a given
3639    period of time. The offset to apply at any given time is found by
3640    locating the observance that has the last onset date and time before
3641    the time in question, and using the offset value from that
3642
3643
3644
3645 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 63]</span>
3646 </pre><pre class="newpage"><a name="page-64" id="page-64" href="#page-64" class="invisible"> </a>
3647 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3648
3649
3650    observance.
3651
3652    The top-level properties in a "VTIMEZONE" calendar component are:
3653
3654    The mandatory "TZID" property is a text value that uniquely
3655    identifies the VTIMZONE calendar component within the scope of an
3656    iCalendar object.
3657
3658    The optional "LAST-MODIFIED" property is a UTC value that specifies
3659    the date and time that this time zone definition was last updated.
3660
3661    The optional "TZURL" property is url value that points to a published
3662    VTIMEZONE definition. TZURL SHOULD refer to a resource that is
3663    accessible by anyone who might need to interpret the object. This
3664    SHOULD NOT normally be a file: URL or other URL that is not widely-
3665    accessible.
3666
3667    The collection of properties that are used to define the STANDARD and
3668    DAYLIGHT sub-components include:
3669
3670    The mandatory "DTSTART" property gives the effective onset date and
3671    local time for the time zone sub-component definition. "DTSTART" in
3672    this usage MUST be specified as a local DATE-TIME value.
3673
3674    The mandatory "TZOFFSETFROM" property gives the UTC offset which is
3675    in use when the onset of this time zone observance begins.
3676    "TZOFFSETFROM" is combined with "DTSTART" to define the effective
3677    onset for the time zone sub-component definition. For example, the
3678    following represents the time at which the observance of Standard
3679    Time took effect in Fall 1967 for New York City:
3680
3681      DTSTART:19671029T020000
3682
3683      TZOFFSETFROM:-0400
3684
3685    The mandatory "TZOFFSETTO " property gives the UTC offset for the
3686    time zone sub-component (Standard Time or Daylight Saving Time) when
3687    this observance is in use.
3688
3689    The optional "TZNAME" property is the customary name for the time
3690    zone. It may be specified multiple times, to allow for specifying
3691    multiple language variants of the time zone names. This could be used
3692    for displaying dates.
3693
3694    If specified, the onset for the observance defined by the time zone
3695    sub-component is defined by either the "RRULE" or "RDATE" property.
3696    If neither is specified, only one sub-component can be specified in
3697    the "VTIMEZONE" calendar component and it is assumed that the single
3698
3699
3700
3701 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 64]</span>
3702 </pre><pre class="newpage"><a name="page-65" id="page-65" href="#page-65" class="invisible"> </a>
3703 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3704
3705
3706    observance specified is always in effect.
3707
3708    The "RRULE" property defines the recurrence rule for the onset of the
3709    observance defined by this time zone sub-component. Some specific
3710    requirements for the usage of RRULE for this purpose include:
3711
3712         - If observance is known to have an effective end date, the
3713         "UNTIL" recurrence rule parameter MUST be used to specify the
3714         last valid onset of this observance (i.e., the UNTIL date-time
3715         will be equal to the last instance generated by the recurrence
3716         pattern). It MUST be specified in UTC time.
3717
3718         - The "DTSTART" and the "TZOFFSETTO" properties MUST be used
3719         when generating the onset date-time values (instances) from the
3720         RRULE.
3721
3722    Alternatively, the "RDATE" property can be used to define the onset
3723    of the observance by giving the individual onset date and times.
3724    "RDATE" in this usage MUST be specified as a local DATE-TIME value in
3725    UTC time.
3726
3727    The optional "COMMENT" property is also allowed for descriptive
3728    explanatory text.
3729
3730    Example: The following are examples of the "VTIMEZONE" calendar
3731    component:
3732
3733    This is an example showing time zone information for the Eastern
3734    United States using "RDATE" property. Note that this is only suitable
3735    for a recurring event that starts on or later than April 6, 1997 at
3736    03:00:00 EDT (i.e., the earliest effective transition date and time)
3737    and ends no later than April 7, 1998 02:00:00 EST (i.e., latest valid
3738    date and time for EST in this scenario). For example, this can be
3739    used for a recurring event that occurs every Friday, 8am-9:00 AM,
3740    starting June 1, 1997, ending December 31, 1997.
3741
3742      BEGIN:VTIMEZONE
3743      TZID:US-Eastern
3744      LAST-MODIFIED:19870101T000000Z
3745      BEGIN:STANDARD
3746      DTSTART:19971026T020000
3747      RDATE:19971026T020000
3748      TZOFFSETFROM:-0400
3749      TZOFFSETTO:-0500
3750      TZNAME:EST
3751      END:STANDARD
3752      BEGIN:DAYLIGHT
3753      DTSTART:19971026T020000
3754
3755
3756
3757 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 65]</span>
3758 </pre><pre class="newpage"><a name="page-66" id="page-66" href="#page-66" class="invisible"> </a>
3759 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3760
3761
3762      RDATE:19970406T020000
3763      TZOFFSETFROM:-0500
3764      TZOFFSETTO:-0400
3765      TZNAME:EDT
3766      END:DAYLIGHT
3767      END:VTIMEZONE
3768
3769    This is a simple example showing the current time zone rules for the
3770    Eastern United States using a RRULE recurrence pattern. Note that
3771    there is no effective end date to either of the Standard Time or
3772    Daylight Time rules. This information would be valid for a recurring
3773    event starting today and continuing indefinitely.
3774
3775      BEGIN:VTIMEZONE
3776      TZID:US-Eastern
3777      LAST-MODIFIED:19870101T000000Z
3778      TZURL:http://zones.stds_r_us.net/tz/US-Eastern
3779      BEGIN:STANDARD
3780      DTSTART:19671029T020000
3781      RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
3782      TZOFFSETFROM:-0400
3783      TZOFFSETTO:-0500
3784      TZNAME:EST
3785      END:STANDARD
3786      BEGIN:DAYLIGHT
3787      DTSTART:19870405T020000
3788      RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
3789      TZOFFSETFROM:-0500
3790      TZOFFSETTO:-0400
3791      TZNAME:EDT
3792      END:DAYLIGHT
3793      END:VTIMEZONE
3794
3795    This is an example showing a fictitious set of rules for the Eastern
3796    United States, where the Daylight Time rule has an effective end date
3797    (i.e., after that date, Daylight Time is no longer observed).
3798
3799      BEGIN:VTIMEZONE
3800      TZID:US--Fictitious-Eastern
3801      LAST-MODIFIED:19870101T000000Z
3802      BEGIN:STANDARD
3803      DTSTART:19671029T020000
3804      RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
3805      TZOFFSETFROM:-0400
3806      TZOFFSETTO:-0500
3807      TZNAME:EST
3808      END:STANDARD
3809
3810
3811
3812
3813 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 66]</span>
3814 </pre><pre class="newpage"><a name="page-67" id="page-67" href="#page-67" class="invisible"> </a>
3815 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3816
3817
3818      BEGIN:DAYLIGHT
3819      DTSTART:19870405T020000
3820      RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4;UNTIL=19980404T070000Z
3821      TZOFFSETFROM:-0500
3822      TZOFFSETTO:-0400
3823      TZNAME:EDT
3824      END:DAYLIGHT
3825      END:VTIMEZONE
3826
3827    This is an example showing a fictitious set of rules for the Eastern
3828    United States, where the first Daylight Time rule has an effective
3829    end date. There is a second Daylight Time rule that picks up where
3830    the other left off.
3831
3832      BEGIN:VTIMEZONE
3833      TZID:US--Fictitious-Eastern
3834      LAST-MODIFIED:19870101T000000Z
3835      BEGIN:STANDARD
3836      DTSTART:19671029T020000
3837      RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
3838      TZOFFSETFROM:-0400
3839      TZOFFSETTO:-0500
3840      TZNAME:EST
3841      END:STANDARD
3842      BEGIN:DAYLIGHT
3843      DTSTART:19870405T020000
3844      RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4;UNTIL=19980404T070000Z
3845      TZOFFSETFROM:-0500
3846      TZOFFSETTO:-0400
3847      TZNAME:EDT
3848      END:DAYLIGHT
3849      BEGIN:DAYLIGHT
3850      DTSTART:19990424T020000
3851      RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=4
3852      TZOFFSETFROM:-0500
3853      TZOFFSETTO:-0400
3854      TZNAME:EDT
3855      END:DAYLIGHT
3856      END:VTIMEZONE
3857
3858 <span class="h4"><h4><a name="section-4.6.6">4.6.6</a> Alarm Component</h4></span>
3859
3860    Component Name: VALARM
3861
3862    Purpose: Provide a grouping of component properties that define an
3863    alarm.
3864
3865
3866
3867
3868
3869 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 67]</span>
3870 </pre><pre class="newpage"><a name="page-68" id="page-68" href="#page-68" class="invisible"> </a>
3871 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3872
3873
3874    Formal Definition: A "VALARM" calendar component is defined by the
3875    following notation:
3876
3877           alarmc     = "BEGIN" ":" "VALARM" CRLF
3878                        (audioprop / dispprop / emailprop / procprop)
3879                        "END" ":" "VALARM" CRLF
3880
3881      audioprop  = 2*(
3882
3883                 ; 'action' and 'trigger' are both REQUIRED,
3884                 ; but MUST NOT occur more than once
3885
3886                 action / trigger /
3887
3888                 ; 'duration' and 'repeat' are both optional,
3889                 ; and MUST NOT occur more than once each,
3890                 ; but if one occurs, so MUST the other
3891
3892                 duration / repeat /
3893
3894                 ; the following is optional,
3895                 ; but MUST NOT occur more than once
3896
3897                 attach /
3898
3899                 ; the following is optional,
3900                 ; and MAY occur more than once
3901
3902                 x-prop
3903
3904                 )
3905
3906
3907
3908      dispprop   = 3*(
3909
3910                 ; the following are all REQUIRED,
3911                 ; but MUST NOT occur more than once
3912
3913                 action / description / trigger /
3914
3915                 ; 'duration' and 'repeat' are both optional,
3916                 ; and MUST NOT occur more than once each,
3917                 ; but if one occurs, so MUST the other
3918
3919                 duration / repeat /
3920
3921                 ; the following is optional,
3922
3923
3924
3925 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 68]</span>
3926 </pre><pre class="newpage"><a name="page-69" id="page-69" href="#page-69" class="invisible"> </a>
3927 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3928
3929
3930                 ; and MAY occur more than once
3931
3932                 *x-prop
3933
3934                 )
3935
3936
3937
3938      emailprop  = 5*(
3939
3940                 ; the following are all REQUIRED,
3941                 ; but MUST NOT occur more than once
3942
3943                 action / description / trigger / summary
3944
3945                 ; the following is REQUIRED,
3946                 ; and MAY occur more than once
3947
3948                 attendee /
3949
3950                 ; 'duration' and 'repeat' are both optional,
3951                 ; and MUST NOT occur more than once each,
3952                 ; but if one occurs, so MUST the other
3953
3954                 duration / repeat /
3955
3956                 ; the following are optional,
3957                 ; and MAY occur more than once
3958
3959                 attach / x-prop
3960
3961                 )
3962
3963
3964
3965      procprop   = 3*(
3966
3967                 ; the following are all REQUIRED,
3968                 ; but MUST NOT occur more than once
3969
3970                 action / attach / trigger /
3971
3972                 ; 'duration' and 'repeat' are both optional,
3973                 ; and MUST NOT occur more than once each,
3974                 ; but if one occurs, so MUST the other
3975
3976                 duration / repeat /
3977
3978
3979
3980
3981 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 69]</span>
3982 </pre><pre class="newpage"><a name="page-70" id="page-70" href="#page-70" class="invisible"> </a>
3983 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
3984
3985
3986                 ; 'description' is optional,
3987                 ; and MUST NOT occur more than once
3988
3989                 description /
3990
3991                 ; the following is optional,
3992                 ; and MAY occur more than once
3993
3994                 x-prop
3995
3996                 )
3997
3998    Description: A "VALARM" calendar component is a grouping of component
3999    properties that is a reminder or alarm for an event or a to-do. For
4000    example, it may be used to define a reminder for a pending event or
4001    an overdue to-do.
4002
4003    The "VALARM" calendar component MUST include the "ACTION" and
4004    "TRIGGER" properties. The "ACTION" property further constrains the
4005    "VALARM" calendar component in the following ways:
4006
4007    When the action is "AUDIO", the alarm can also include one and only
4008    one "ATTACH" property, which MUST point to a sound resource, which is
4009    rendered when the alarm is triggered.
4010
4011    When the action is "DISPLAY", the alarm MUST also include a
4012    "DESCRIPTION" property, which contains the text to be displayed when
4013    the alarm is triggered.
4014
4015    When the action is "EMAIL", the alarm MUST include a "DESCRIPTION"
4016    property, which contains the text to be used as the message body, a
4017    "SUMMARY" property, which contains the text to be used as the message
4018    subject, and one or more "ATTENDEE" properties, which contain the
4019    email address of attendees to receive the message. It can also
4020    include one or more "ATTACH" properties, which are intended to be
4021    sent as message attachments. When the alarm is triggered, the email
4022    message is sent.
4023
4024    When the action is "PROCEDURE", the alarm MUST include one and only
4025    one "ATTACH" property, which MUST point to a procedure resource,
4026    which is invoked when the alarm is triggered.
4027
4028    The "VALARM" calendar component MUST only appear within either a
4029    "VEVENT" or "VTODO" calendar component. "VALARM" calendar components
4030    cannot be nested. Multiple mutually independent "VALARM" calendar
4031    components can be specified for a single "VEVENT" or "VTODO" calendar
4032    component.
4033
4034
4035
4036
4037 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 70]</span>
4038 </pre><pre class="newpage"><a name="page-71" id="page-71" href="#page-71" class="invisible"> </a>
4039 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4040
4041
4042    The "TRIGGER" property specifies when the alarm will be triggered.
4043    The "TRIGGER" property specifies a duration prior to the start of an
4044    event or a to-do. The "TRIGGER" edge may be explicitly set to be
4045    relative to the "START" or "END" of the event or to-do with the
4046    "RELATED" parameter of the "TRIGGER" property. The "TRIGGER" property
4047    value type can alternatively be set to an absolute calendar date and
4048    time of day value.
4049
4050    In an alarm set to trigger on the "START" of an event or to-do, the
4051    "DTSTART" property MUST be present in the associated event or to-do.
4052    In an alarm in a "VEVENT" calendar component set to trigger on the
4053    "END" of the event, either the "DTEND" property MUST be present, or
4054    the "DTSTART" and "DURATION" properties MUST both be present. In an
4055    alarm in a "VTODO" calendar component set to trigger on the "END" of
4056    the to-do, either the "DUE" property MUST be present, or the
4057    "DTSTART" and "DURATION" properties MUST both be present.
4058
4059    The alarm can be defined such that it triggers repeatedly. A
4060    definition of an alarm with a repeating trigger MUST include both the
4061    "DURATION" and "REPEAT" properties. The "DURATION" property specifies
4062    the delay period, after which the alarm will repeat. The "REPEAT"
4063    property specifies the number of additional repetitions that the
4064    alarm will triggered. This repitition count is in addition to the
4065    initial triggering of the alarm. Both of these properties MUST be
4066    present in order to specify a repeating alarm. If one of these two
4067    properties is absent, then the alarm will not repeat beyond the
4068    initial trigger.
4069
4070    The "ACTION" property is used within the "VALARM" calendar component
4071    to specify the type of action invoked when the alarm is triggered.
4072    The "VALARM" properties provide enough information for a specific
4073    action to be invoked. It is typically the responsibility of a
4074    "Calendar User Agent" (CUA) to deliver the alarm in the specified
4075    fashion. An "ACTION" property value of AUDIO specifies an alarm that
4076    causes a sound to be played to alert the user; DISPLAY specifies an
4077    alarm that causes a text message to be displayed to the user; EMAIL
4078    specifies an alarm that causes an electronic email message to be
4079    delivered to one or more email addresses; and PROCEDURE specifies an
4080    alarm that causes a procedure to be executed. The "ACTION" property
4081    MUST specify one and only one of these values.
4082
4083    In an AUDIO alarm, if the optional "ATTACH" property is included, it
4084    MUST specify an audio sound resource. The intention is that the sound
4085    will be played as the alarm effect. If an "ATTACH" property is
4086    specified that does not refer to a sound resource, or if the
4087    specified sound resource cannot be rendered (because its format is
4088    unsupported, or because it cannot be retrieved), then the CUA or
4089    other entity responsible for playing the sound may choose a fallback
4090
4091
4092
4093 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 71]</span>
4094 </pre><pre class="newpage"><a name="page-72" id="page-72" href="#page-72" class="invisible"> </a>
4095 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4096
4097
4098    action, such as playing a built-in default sound, or playing no sound
4099    at all.
4100
4101    In a DISPLAY alarm, the intended alarm effect is for the text value
4102    of the "DESCRIPTION" property to be displayed to the user.
4103
4104    In an EMAIL alarm, the intended alarm effect is for an email message
4105    to be composed and delivered to all the addresses specified by the
4106    "ATTENDEE" properties in the "VALARM" calendar component. The
4107    "DESCRIPTION" property of the "VALARM" calendar component MUST be
4108    used as the body text of the message, and the "SUMMARY" property MUST
4109    be used as the subject text. Any "ATTACH" properties in the "VALARM"
4110    calendar component SHOULD be sent as attachments to the message.
4111
4112    In a PROCEDURE alarm, the "ATTACH" property in the "VALARM" calendar
4113    component MUST specify a procedure or program that is intended to be
4114    invoked as the alarm effect. If the procedure or program is in a
4115    format that cannot be rendered, then no procedure alarm will be
4116    invoked. If the "DESCRIPTION" property is present, its value
4117    specifies the argument string to be passed to the procedure or
4118    program. "Calendar User Agents" that receive an iCalendar object with
4119    this category of alarm, can disable or allow the "Calendar User" to
4120    disable, or otherwise ignore this type of alarm. While a very useful
4121    alarm capability, the PROCEDURE type of alarm SHOULD be treated by
4122    the "Calendar User Agent" as a potential security risk.
4123
4124    Example: The following example is for a "VALARM" calendar component
4125    that specifies an audio alarm that will sound at a precise time and
4126    repeat 4 more times at 15 minute intervals:
4127
4128      BEGIN:VALARM
4129      TRIGGER;VALUE=DATE-TIME:19970317T133000Z
4130      REPEAT:4
4131      DURATION:PT15M
4132      ACTION:AUDIO
4133      ATTACH;FMTTYPE=audio/basic:ftp://host.com/pub/sounds/bell-01.aud
4134      END:VALARM
4135
4136    The following example is for a "VALARM" calendar component that
4137    specifies a display alarm that will trigger 30 minutes before the
4138    scheduled start of the event or the due date/time of the to-do it is
4139    associated with and will repeat 2 more times at 15 minute intervals:
4140
4141      BEGIN:VALARM
4142      TRIGGER:-PT30M
4143      REPEAT:2
4144      DURATION:PT15M
4145      ACTION:DISPLAY
4146
4147
4148
4149 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 72]</span>
4150 </pre><pre class="newpage"><a name="page-73" id="page-73" href="#page-73" class="invisible"> </a>
4151 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4152
4153
4154      DESCRIPTION:Breakfast meeting with executive\n
4155       team at 8:30 AM EST.
4156      END:VALARM
4157
4158    The following example is for a "VALARM" calendar component that
4159    specifies an email alarm that will trigger 2 days before the
4160    scheduled due date/time of a to-do it is associated with. It does not
4161    repeat. The email has a subject, body and attachment link.
4162
4163      BEGIN:VALARM
4164      TRIGGER:-P2D
4165      ACTION:EMAIL
4166      ATTENDEE:MAILTO:john_doe@host.com
4167      SUMMARY:*** REMINDER: SEND AGENDA FOR WEEKLY STAFF MEETING ***
4168      DESCRIPTION:A draft agenda needs to be sent out to the attendees
4169        to the weekly managers meeting (MGR-LIST). Attached is a
4170        pointer the document template for the agenda file.
4171      ATTACH;FMTTYPE=application/binary:http://host.com/templates/agen
4172       da.doc
4173      END:VALARM
4174
4175    The following example is for a "VALARM" calendar component that
4176    specifies a procedural alarm that will trigger at a precise date/time
4177    and will repeat 23 more times at one hour intervals. The alarm will
4178    invoke a procedure file.
4179
4180      BEGIN:VALARM
4181      TRIGGER;VALUE=DATE-TIME:19980101T050000Z
4182      REPEAT:23
4183      DURATION:PT1H
4184      ACTION:PROCEDURE
4185      ATTACH;FMTTYPE=application/binary:ftp://host.com/novo-
4186       procs/felizano.exe
4187      END:VALARM
4188
4189 <span class="h3"><h3><a name="section-4.7">4.7</a> Calendar Properties</h3></span>
4190
4191    The Calendar Properties are attributes that apply to the iCalendar
4192    object, as a whole. These properties do not appear within a calendar
4193    component. They SHOULD be specified after the "BEGIN:VCALENDAR"
4194    property and prior to any calendar component.
4195
4196 <span class="h4"><h4><a name="section-4.7.1">4.7.1</a> Calendar Scale</h4></span>
4197
4198    Property Name: CALSCALE
4199
4200    Purpose: This property defines the calendar scale used for the
4201    calendar information specified in the iCalendar object.
4202
4203
4204
4205 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 73]</span>
4206 </pre><pre class="newpage"><a name="page-74" id="page-74" href="#page-74" class="invisible"> </a>
4207 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4208
4209
4210    Value Type: TEXT
4211
4212    Property Parameters: Non-standard property parameters can be
4213    specified on this property.
4214
4215    Conformance: Property can be specified in an iCalendar object. The
4216    default value is "GREGORIAN".
4217
4218    Description: This memo is based on the Gregorian calendar scale. The
4219    Gregorian calendar scale is assumed if this property is not specified
4220    in the iCalendar object. It is expected that other calendar scales
4221    will be defined in other specifications or by future versions of this
4222    memo.
4223
4224    Format Definition: The property is defined by the following notation:
4225
4226      calscale   = "CALSCALE" calparam ":" calvalue CRLF
4227
4228      calparam   = *(";" xparam)
4229
4230      calvalue   = "GREGORIAN" / iana-token
4231
4232    Example: The following is an example of this property:
4233
4234      CALSCALE:GREGORIAN
4235
4236 <span class="h4"><h4><a name="section-4.7.2">4.7.2</a> Method</h4></span>
4237
4238    Property Name: METHOD
4239
4240    Purpose: This property defines the iCalendar object method associated
4241    with the calendar object.
4242
4243    Value Type: TEXT
4244
4245    Property Parameters: Non-standard property parameters can be
4246    specified on this property.
4247
4248    Conformance: The property can be specified in an iCalendar object.
4249
4250    Description: When used in a MIME message entity, the value of this
4251    property MUST be the same as the Content-Type "method" parameter
4252    value. This property can only appear once within the iCalendar
4253    object. If either the "METHOD" property or the Content-Type "method"
4254    parameter is specified, then the other MUST also be specified.
4255
4256    No methods are defined by this specification. This is the subject of
4257    other specifications, such as the iCalendar Transport-independent
4258
4259
4260
4261 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 74]</span>
4262 </pre><pre class="newpage"><a name="page-75" id="page-75" href="#page-75" class="invisible"> </a>
4263 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4264
4265
4266    Interoperability Protocol (iTIP) defined by [<a href="#ref-ITIP" title="&quot;iCalendar Transport-Independent Interoperability Protocol (iTIP) : Scheduling Events, Busy Time, To-dos and Journal Entries&quot;">ITIP</a>].
4267
4268    If this property is not present in the iCalendar object, then a
4269    scheduling transaction MUST NOT be assumed. In such cases, the
4270    iCalendar object is merely being used to transport a snapshot of some
4271    calendar information; without the intention of conveying a scheduling
4272    semantic.
4273
4274    Format Definition: The property is defined by the following notation:
4275
4276      method     = "METHOD" metparam ":" metvalue CRLF
4277
4278      metparam   = *(";" xparam)
4279
4280      metvalue   = iana-token
4281
4282    Example: The following is a hypothetical example of this property to
4283    convey that the iCalendar object is a request for a meeting:
4284
4285      METHOD:REQUEST
4286
4287 <span class="h4"><h4><a name="section-4.7.3">4.7.3</a> Product Identifier</h4></span>
4288
4289    Property Name: PRODID
4290
4291    Purpose: This property specifies the identifier for the product that
4292    created the iCalendar object.
4293
4294    Value Type: TEXT
4295
4296    Property Parameters: Non-standard property parameters can be
4297    specified on this property.
4298
4299    Conformance: The property MUST be specified once in an iCalendar
4300    object.
4301
4302    Description: The vendor of the implementation SHOULD assure that this
4303    is a globally unique identifier; using some technique such as an FPI
4304    value, as defined in [ISO 9070].
4305
4306    This property SHOULD not be used to alter the interpretation of an
4307    iCalendar object beyond the semantics specified in this memo. For
4308    example, it is not to be used to further the understanding of non-
4309    standard properties.
4310
4311    Format Definition: The property is defined by the following notation:
4312
4313      prodid     = "PRODID" pidparam ":" pidvalue CRLF
4314
4315
4316
4317 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 75]</span>
4318 </pre><pre class="newpage"><a name="page-76" id="page-76" href="#page-76" class="invisible"> </a>
4319 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4320
4321
4322      pidparam   = *(";" xparam)
4323
4324      pidvalue   = text
4325      ;Any text that describes the product and version
4326      ;and that is generally assured of being unique.
4327
4328    Example: The following is an example of this property. It does not
4329    imply that English is the default language.
4330
4331      PRODID:-//ABC Corporation//NONSGML My Product//EN
4332
4333 <span class="h4"><h4><a name="section-4.7.4">4.7.4</a> Version</h4></span>
4334
4335    Property Name: VERSION
4336
4337    Purpose: This property specifies the identifier corresponding to the
4338    highest version number or the minimum and maximum range of the
4339    iCalendar specification that is required in order to interpret the
4340    iCalendar object.
4341
4342    Value Type: TEXT
4343
4344    Property Parameters: Non-standard property parameters can be
4345    specified on this property.
4346
4347    Conformance: This property MUST be specified by an iCalendar object,
4348    but MUST only be specified once.
4349
4350    Description: A value of "2.0" corresponds to this memo.
4351
4352    Format Definition: The property is defined by the following notation:
4353
4354      version    = "VERSION" verparam ":" vervalue CRLF
4355
4356      verparam   = *(";" xparam)
4357
4358      vervalue   = "2.0"         ;This memo
4359                 / maxver
4360                 / (minver ";" maxver)
4361
4362      minver     = &lt;A IANA registered iCalendar version identifier&gt;
4363      ;Minimum iCalendar version needed to parse the iCalendar object
4364
4365      maxver     = &lt;A IANA registered iCalendar version identifier&gt;
4366      ;Maximum iCalendar version needed to parse the iCalendar object
4367
4368    Example: The following is an example of this property:
4369
4370
4371
4372
4373 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 76]</span>
4374 </pre><pre class="newpage"><a name="page-77" id="page-77" href="#page-77" class="invisible"> </a>
4375 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4376
4377
4378      VERSION:2.0
4379
4380 <span class="h3"><h3><a name="section-4.8">4.8</a> Component Properties</h3></span>
4381
4382    The following properties can appear within calendar components, as
4383    specified by each component property definition.
4384
4385 <span class="h4"><h4><a name="section-4.8.1">4.8.1</a> Descriptive Component Properties</h4></span>
4386
4387    The following properties specify descriptive information about
4388    calendar components.
4389
4390 <span class="h5"><h5><a name="section-4.8.1.1">4.8.1.1</a> Attachment</h5></span>
4391
4392    Property Name: ATTACH
4393
4394    Purpose: The property provides the capability to associate a document
4395    object with a calendar component.
4396
4397    Value Type: The default value type for this property is URI. The
4398    value type can also be set to BINARY to indicate inline binary
4399    encoded content information.
4400
4401    Property Parameters: Non-standard, inline encoding, format type and
4402    value data type property parameters can be specified on this
4403    property.
4404
4405    Conformance: The property can be specified in a "VEVENT", "VTODO",
4406    "VJOURNAL" or "VALARM" calendar components.
4407
4408    Description: The property can be specified within "VEVENT", "VTODO",
4409    "VJOURNAL", or "VALARM" calendar components. This property can be
4410    specified multiple times within an iCalendar object.
4411
4412    Format Definition: The property is defined by the following notation:
4413
4414      attach     = "ATTACH" attparam ":" uri  CRLF
4415
4416      attach     =/ "ATTACH" attparam ";" "ENCODING" "=" "BASE64"
4417                    ";" "VALUE" "=" "BINARY" ":" binary
4418
4419      attparam   = *(
4420
4421                 ; the following is optional,
4422                 ; but MUST NOT occur more than once
4423
4424                 (";" fmttypeparam) /
4425
4426
4427
4428
4429 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 77]</span>
4430 </pre><pre class="newpage"><a name="page-78" id="page-78" href="#page-78" class="invisible"> </a>
4431 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4432
4433
4434                 ; the following is optional,
4435                 ; and MAY occur more than once
4436
4437                 (";" xparam)
4438
4439                 )
4440
4441    Example: The following are examples of this property:
4442
4443      ATTACH:CID:jsmith.part3.960817T083000.xyzMail@host1.com
4444
4445      ATTACH;FMTTYPE=application/postscript:ftp://xyzCorp.com/pub/
4446       reports/r-960812.ps
4447
4448 <span class="h5"><h5><a name="section-4.8.1.2">4.8.1.2</a> Categories</h5></span>
4449
4450    Property Name: CATEGORIES
4451
4452    Purpose: This property defines the categories for a calendar
4453    component.
4454
4455    Value Type: TEXT
4456
4457    Property Parameters: Non-standard and language property parameters
4458    can be specified on this property.
4459
4460    Conformance: The property can be specified within "VEVENT", "VTODO"
4461    or "VJOURNAL" calendar components.
4462
4463    Description: This property is used to specify categories or subtypes
4464    of the calendar component. The categories are useful in searching for
4465    a calendar component of a particular type and category. Within the
4466    "VEVENT", "VTODO" or "VJOURNAL" calendar components, more than one
4467    category can be specified as a list of categories separated by the
4468    COMMA character (US-ASCII decimal 44).
4469
4470    Format Definition: The property is defined by the following notation:
4471
4472      categories = "CATEGORIES" catparam ":" text *("," text)
4473                   CRLF
4474
4475      catparam   = *(
4476
4477                 ; the following is optional,
4478                 ; but MUST NOT occur more than once
4479
4480                 (";" languageparam ) /
4481
4482
4483
4484
4485 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 78]</span>
4486 </pre><pre class="newpage"><a name="page-79" id="page-79" href="#page-79" class="invisible"> </a>
4487 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4488
4489
4490                 ; the following is optional,
4491                 ; and MAY occur more than once
4492
4493                 (";" xparam)
4494
4495                 )
4496
4497    Example: The following are examples of this property:
4498
4499      CATEGORIES:APPOINTMENT,EDUCATION
4500
4501      CATEGORIES:MEETING
4502
4503 <span class="h5"><h5><a name="section-4.8.1.3">4.8.1.3</a> Classification</h5></span>
4504
4505    Property Name: CLASS
4506
4507    Purpose: This property defines the access classification for a
4508    calendar component.
4509
4510    Value Type: TEXT
4511
4512    Property Parameters: Non-standard property parameters can be
4513    specified on this property.
4514
4515    Conformance: The property can be specified once in a "VEVENT",
4516    "VTODO" or "VJOURNAL" calendar components.
4517
4518    Description: An access classification is only one component of the
4519    general security system within a calendar application. It provides a
4520    method of capturing the scope of the access the calendar owner
4521    intends for information within an individual calendar entry. The
4522    access classification of an individual iCalendar component is useful
4523    when measured along with the other security components of a calendar
4524    system (e.g., calendar user authentication, authorization, access
4525    rights, access role, etc.). Hence, the semantics of the individual
4526    access classifications cannot be completely defined by this memo
4527    alone. Additionally, due to the "blind" nature of most exchange
4528    processes using this memo, these access classifications cannot serve
4529    as an enforcement statement for a system receiving an iCalendar
4530    object. Rather, they provide a method for capturing the intention of
4531    the calendar owner for the access to the calendar component.
4532
4533    Format Definition: The property is defined by the following notation:
4534
4535      class      = "CLASS" classparam ":" classvalue CRLF
4536
4537      classparam = *(";" xparam)
4538
4539
4540
4541 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 79]</span>
4542 </pre><pre class="newpage"><a name="page-80" id="page-80" href="#page-80" class="invisible"> </a>
4543 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4544
4545
4546      classvalue = "PUBLIC" / "PRIVATE" / "CONFIDENTIAL" / iana-token
4547                 / x-name
4548      ;Default is PUBLIC
4549
4550    Example: The following is an example of this property:
4551
4552      CLASS:PUBLIC
4553
4554 <span class="h5"><h5><a name="section-4.8.1.4">4.8.1.4</a> Comment</h5></span>
4555
4556    Property Name: COMMENT
4557
4558    Purpose: This property specifies non-processing information intended
4559    to provide a comment to the calendar user.
4560
4561    Value Type: TEXT
4562
4563    Property Parameters: Non-standard, alternate text representation and
4564    language property parameters can be specified on this property.
4565
4566    Conformance: This property can be specified in "VEVENT", "VTODO",
4567    "VJOURNAL", "VTIMEZONE" or "VFREEBUSY" calendar components.
4568
4569    Description: The property can be specified multiple times.
4570
4571    Format Definition: The property is defined by the following notation:
4572
4573      comment    = "COMMENT" commparam ":" text CRLF
4574
4575      commparam  = *(
4576
4577                 ; the following are optional,
4578                 ; but MUST NOT occur more than once
4579
4580                 (";" altrepparam) / (";" languageparam) /
4581
4582                 ; the following is optional,
4583                 ; and MAY occur more than once
4584
4585                 (";" xparam)
4586
4587                 )
4588
4589    Example: The following is an example of this property:
4590
4591      COMMENT:The meeting really needs to include both ourselves
4592        and the customer. We can't hold this  meeting without them.
4593        As a matter of fact\, the venue for the meeting ought to be at
4594
4595
4596
4597 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 80]</span>
4598 </pre><pre class="newpage"><a name="page-81" id="page-81" href="#page-81" class="invisible"> </a>
4599 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4600
4601
4602        their site. - - John
4603
4604    The data type for this property is TEXT.
4605
4606 <span class="h5"><h5><a name="section-4.8.1.5">4.8.1.5</a> Description</h5></span>
4607
4608    Property Name: DESCRIPTION
4609
4610    Purpose: This property provides a more complete description of the
4611    calendar component, than that provided by the "SUMMARY" property.
4612
4613    Value Type: TEXT
4614
4615    Property Parameters: Non-standard, alternate text representation and
4616    language property parameters can be specified on this property.
4617
4618    Conformance: The property can be specified in the "VEVENT", "VTODO",
4619    "VJOURNAL" or "VALARM" calendar components. The property can be
4620    specified multiple times only within a "VJOURNAL" calendar component.
4621
4622    Description: This property is used in the "VEVENT" and "VTODO" to
4623    capture lengthy textual decriptions associated with the activity.
4624
4625    This property is used in the "VJOURNAL" calendar component to capture
4626    one more textual journal entries.
4627
4628    This property is used in the "VALARM" calendar component to capture
4629    the display text for a DISPLAY category of alarm, to capture the body
4630    text for an EMAIL category of alarm and to capture the argument
4631    string for a PROCEDURE category of alarm.
4632
4633    Format Definition: The property is defined by the following notation:
4634
4635      description        = "DESCRIPTION" descparam ":" text CRLF
4636
4637      descparam  = *(
4638
4639                 ; the following are optional,
4640                 ; but MUST NOT occur more than once
4641
4642                 (";" altrepparam) / (";" languageparam) /
4643
4644                 ; the following is optional,
4645                 ; and MAY occur more than once
4646
4647                 (";" xparam)
4648
4649                 )
4650
4651
4652
4653 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 81]</span>
4654 </pre><pre class="newpage"><a name="page-82" id="page-82" href="#page-82" class="invisible"> </a>
4655 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4656
4657
4658    Example: The following is an example of the property with formatted
4659    line breaks in the property value:
4660
4661      DESCRIPTION:Meeting to provide technical review for "Phoenix"
4662        design.\n Happy Face Conference Room. Phoenix design team
4663        MUST attend this meeting.\n RSVP to team leader.
4664
4665    The following is an example of the property with folding of long
4666    lines:
4667
4668      DESCRIPTION:Last draft of the new novel is to be completed
4669        for the editor's proof today.
4670
4671 <span class="h5"><h5><a name="section-4.8.1.6">4.8.1.6</a> Geographic Position</h5></span>
4672
4673    Property Name: GEO
4674
4675    Purpose: This property specifies information related to the global
4676    position for the activity specified by a calendar component.
4677
4678    Value Type: FLOAT. The value MUST be two SEMICOLON separated FLOAT
4679    values.
4680
4681    Property Parameters: Non-standard property parameters can be
4682    specified on this property.
4683
4684    Conformance: This property can be specified in  "VEVENT" or "VTODO"
4685    calendar components.
4686
4687    Description: The property value specifies latitude and longitude, in
4688    that order (i.e., "LAT LON" ordering). The longitude represents the
4689    location east or west of the prime meridian as a positive or negative
4690    real number, respectively. The longitude and latitude values MAY be
4691    specified up to six decimal places, which will allow for accuracy to
4692    within one meter of geographical position. Receiving applications
4693    MUST accept values of this precision and MAY truncate values of
4694    greater precision.
4695
4696    Values for latitude and longitude shall be expressed as decimal
4697    fractions of degrees. Whole degrees of latitude shall be represented
4698    by a two-digit decimal number ranging from 0 through 90. Whole
4699    degrees of longitude shall be represented by a decimal number ranging
4700    from 0 through 180. When a decimal fraction of a degree is specified,
4701    it shall be separated from the whole number of degrees by a decimal
4702    point.
4703
4704
4705
4706
4707
4708
4709 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 82]</span>
4710 </pre><pre class="newpage"><a name="page-83" id="page-83" href="#page-83" class="invisible"> </a>
4711 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4712
4713
4714    Latitudes north of the equator shall be specified by a plus sign (+),
4715    or by the absence of a minus sign (-), preceding the digits
4716    designating degrees. Latitudes south of the Equator shall be
4717    designated by a minus sign (-) preceding the digits designating
4718    degrees. A point on the Equator shall be assigned to the Northern
4719    Hemisphere.
4720
4721    Longitudes east of the prime meridian shall be specified by a plus
4722    sign (+), or by the absence of a minus sign (-), preceding the digits
4723    designating degrees. Longitudes west of the meridian shall be
4724    designated by minus sign (-) preceding the digits designating
4725    degrees. A point on the prime meridian shall be assigned to the
4726    Eastern Hemisphere. A point on the 180th meridian shall be assigned
4727    to the Western Hemisphere. One exception to this last convention is
4728    permitted. For the special condition of describing a band of latitude
4729    around the earth, the East Bounding Coordinate data element shall be
4730    assigned the value +180 (180) degrees.
4731
4732    Any spatial address with a latitude of +90 (90) or -90 degrees will
4733    specify the position at the North or South Pole, respectively. The
4734    component for longitude may have any legal value.
4735
4736    With the exception of the special condition described above, this
4737    form is specified in Department of Commerce, 1986, Representation of
4738    geographic point locations for information interchange (Federal
4739    Information Processing Standard 70-1):  Washington,  Department of
4740    Commerce, National Institute of Standards and Technology.
4741
4742    The simple formula for converting degrees-minutes-seconds into
4743    decimal degrees is:
4744
4745      decimal = degrees + minutes/60 + seconds/3600.
4746
4747    Format Definition: The property is defined by the following notation:
4748
4749      geo        = "GEO" geoparam ":" geovalue CRLF
4750
4751      geoparam   = *(";" xparam)
4752
4753      geovalue   = float ";" float
4754      ;Latitude and Longitude components
4755
4756    Example: The following is an example of this property:
4757
4758      GEO:37.386013;-122.082932
4759
4760
4761
4762
4763
4764
4765 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 83]</span>
4766 </pre><pre class="newpage"><a name="page-84" id="page-84" href="#page-84" class="invisible"> </a>
4767 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4768
4769
4770 <span class="h5"><h5><a name="section-4.8.1.7">4.8.1.7</a> Location</h5></span>
4771
4772    Property Name: LOCATION
4773
4774    Purpose: The property defines the intended venue for the activity
4775    defined by a calendar component.
4776
4777    Value Type: TEXT
4778
4779    Property Parameters: Non-standard, alternate text representation and
4780    language property parameters can be specified on this property.
4781
4782    Conformance: This property can be specified in "VEVENT" or "VTODO"
4783    calendar component.
4784
4785    Description: Specific venues such as conference or meeting rooms may
4786    be explicitly specified using this property. An alternate
4787    representation may be specified that is a URI that points to
4788    directory information with more structured specification of the
4789    location. For example, the alternate representation may specify
4790    either an LDAP URI pointing to an LDAP server entry or a CID URI
4791    pointing to a MIME body part containing a vCard [<a href="http://tools.ietf.org/html/rfc2426" title="&quot;vCard MIME Directory Profile&quot;">RFC 2426</a>] for the
4792    location.
4793
4794    Format Definition: The property is defined by the following notation:
4795
4796      location   = "LOCATION locparam ":" text CRLF
4797
4798      locparam   = *(
4799
4800                 ; the following are optional,
4801                 ; but MUST NOT occur more than once
4802
4803                 (";" altrepparam) / (";" languageparam) /
4804
4805                 ; the following is optional,
4806                 ; and MAY occur more than once
4807
4808                 (";" xparam)
4809
4810                 )
4811
4812    Example: The following are some examples of this property:
4813
4814      LOCATION:Conference Room - F123, Bldg. 002
4815
4816      LOCATION;ALTREP="http://xyzcorp.com/conf-rooms/f123.vcf":
4817       Conference Room - F123, Bldg. 002
4818
4819
4820
4821 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 84]</span>
4822 </pre><pre class="newpage"><a name="page-85" id="page-85" href="#page-85" class="invisible"> </a>
4823 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4824
4825
4826 <span class="h5"><h5><a name="section-4.8.1.8">4.8.1.8</a> Percent Complete</h5></span>
4827
4828    Property Name: PERCENT-COMPLETE
4829
4830    Purpose: This property is used by an assignee or delegatee of a to-do
4831    to convey the percent completion of a to-do to the Organizer.
4832
4833    Value Type: INTEGER
4834
4835    Property Parameters: Non-standard property parameters can be
4836    specified on this property.
4837
4838    Conformance: This property can be specified in a "VTODO" calendar
4839    component.
4840
4841    Description: The property value is a positive integer between zero
4842    and one hundred. A value of "0" indicates the to-do has not yet been
4843    started. A value of "100" indicates that the to-do has been
4844    completed. Integer values in between indicate the percent partially
4845    complete.
4846
4847    When a to-do is assigned to multiple individuals, the property value
4848    indicates the percent complete for that portion of the to-do assigned
4849    to the assignee or delegatee. For example, if a to-do is assigned to
4850    both individuals "A" and "B". A reply from "A" with a percent
4851    complete of "70" indicates that "A" has completed 70% of the to-do
4852    assigned to them. A reply from "B" with a percent complete of "50"
4853    indicates "B" has completed 50% of the to-do assigned to them.
4854
4855    Format Definition: The property is defined by the following notation:
4856
4857      percent = "PERCENT-COMPLETE" pctparam ":" integer CRLF
4858
4859      pctparam   = *(";" xparam)
4860
4861    Example: The following is an example of this property to show 39%
4862    completion:
4863
4864      PERCENT-COMPLETE:39
4865
4866 <span class="h5"><h5><a name="section-4.8.1.9">4.8.1.9</a> Priority</h5></span>
4867
4868    Property Name: PRIORITY
4869
4870    Purpose: The property defines the relative priority for a calendar
4871    component.
4872
4873    Value Type: INTEGER
4874
4875
4876
4877 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 85]</span>
4878 </pre><pre class="newpage"><a name="page-86" id="page-86" href="#page-86" class="invisible"> </a>
4879 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4880
4881
4882    Property Parameters: Non-standard property parameters can be
4883    specified on this property.
4884
4885    Conformance: The property can be specified in a "VEVENT" or "VTODO"
4886    calendar component.
4887
4888    Description: The priority is specified as an integer in the range
4889    zero to nine. A value of zero (US-ASCII decimal 48) specifies an
4890    undefined priority. A value of one (US-ASCII decimal 49) is the
4891    highest priority. A value of two (US-ASCII decimal 50) is the second
4892    highest priority. Subsequent numbers specify a decreasing ordinal
4893    priority. A value of nine (US-ASCII decimal 58) is the lowest
4894    priority.
4895
4896    A CUA with a three-level priority scheme of "HIGH", "MEDIUM" and
4897    "LOW" is mapped into this property such that a property value in the
4898    range of one (US-ASCII decimal 49) to four (US-ASCII decimal 52)
4899    specifies "HIGH" priority. A value of five (US-ASCII decimal 53) is
4900    the normal or "MEDIUM" priority. A value in the range of six (US-
4901    ASCII decimal 54) to nine (US-ASCII decimal 58) is "LOW" priority.
4902
4903    A CUA with a priority schema of "A1", "A2", "A3", "B1", "B2", ...,
4904    "C3" is mapped into this property such that a property value of one
4905    (US-ASCII decimal 49) specifies "A1", a property value of two (US-
4906    ASCII decimal 50) specifies "A2", a property value of three (US-ASCII
4907    decimal 51) specifies "A3", and so forth up to a property value of 9
4908    (US-ASCII decimal 58) specifies "C3".
4909
4910    Other integer values are reserved for future use.
4911
4912    Within a "VEVENT" calendar component, this property specifies a
4913    priority for the event. This property may be useful when more than
4914    one event is scheduled for a given time period.
4915
4916    Within a "VTODO" calendar component, this property specified a
4917    priority for the to-do. This property is useful in prioritizing
4918    multiple action items for a given time period.
4919
4920    Format Definition: The property is specified by the following
4921    notation:
4922
4923      priority   = "PRIORITY" prioparam ":" privalue CRLF
4924      ;Default is zero
4925
4926      prioparam  = *(";" xparam)
4927
4928      privalue   = integer       ;Must be in the range [<a href="#ref-0..9">0..9</a>]
4929         ; All other values are reserved for future use
4930
4931
4932
4933 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 86]</span>
4934 </pre><pre class="newpage"><a name="page-87" id="page-87" href="#page-87" class="invisible"> </a>
4935 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4936
4937
4938    The following is an example of a property with the highest priority:
4939
4940      PRIORITY:1
4941
4942    The following is an example of a property with a next highest
4943    priority:
4944
4945      PRIORITY:2
4946
4947    Example: The following is an example of a property with no priority.
4948    This is equivalent to not specifying the "PRIORITY" property:
4949
4950      PRIORITY:0
4951
4952 <span class="h5"><h5><a name="section-4.8.1.10">4.8.1.10</a> Resources</h5></span>
4953
4954    Property Name: RESOURCES
4955
4956    Purpose: This property defines the equipment or resources anticipated
4957    for an activity specified by a calendar entity..
4958
4959    Value Type: TEXT
4960
4961    Property Parameters: Non-standard, alternate text representation and
4962    language property parameters can be specified on this property.
4963
4964    Conformance: This property can be specified in "VEVENT" or "VTODO"
4965    calendar component.
4966
4967    Description: The property value is an arbitrary text. More than one
4968    resource can be specified as a list of resources separated by the
4969    COMMA character (US-ASCII decimal 44).
4970
4971    Format Definition: The property is defined by the following notation:
4972
4973      resources  = "RESOURCES" resrcparam ":" text *("," text) CRLF
4974
4975      resrcparam = *(
4976
4977                 ; the following are optional,
4978                 ; but MUST NOT occur more than once
4979
4980                 (";" altrepparam) / (";" languageparam) /
4981
4982                 ; the following is optional,
4983                 ; and MAY occur more than once
4984
4985
4986
4987
4988
4989 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 87]</span>
4990 </pre><pre class="newpage"><a name="page-88" id="page-88" href="#page-88" class="invisible"> </a>
4991 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
4992
4993
4994                 (";" xparam)
4995
4996                 )
4997
4998    Example: The following is an example of this property:
4999
5000      RESOURCES:EASEL,PROJECTOR,VCR
5001
5002      RESOURCES;LANGUAGE=fr:1 raton-laveur
5003
5004 <span class="h5"><h5><a name="section-4.8.1.11">4.8.1.11</a> Status</h5></span>
5005
5006    Property Name: STATUS
5007
5008    Purpose: This property defines the overall status or confirmation for
5009    the calendar component.
5010
5011    Value Type: TEXT
5012
5013    Property Parameters: Non-standard property parameters can be
5014    specified on this property.
5015
5016    Conformance: This property can be specified in "VEVENT", "VTODO" or
5017    "VJOURNAL" calendar components.
5018
5019    Description: In a group scheduled calendar component, the property is
5020    used by the "Organizer" to provide a confirmation of the event to the
5021    "Attendees". For example in a "VEVENT" calendar component, the
5022    "Organizer" can indicate that a meeting is tentative, confirmed or
5023    cancelled. In a "VTODO" calendar component, the "Organizer" can
5024    indicate that an action item needs action, is completed, is in
5025    process or being worked on, or has been cancelled. In a "VJOURNAL"
5026    calendar component, the "Organizer" can indicate that a journal entry
5027    is draft, final or has been cancelled or removed.
5028
5029    Format Definition: The property is defined by the following notation:
5030
5031      status     = "STATUS" statparam] ":" statvalue CRLF
5032
5033      statparam  = *(";" xparam)
5034
5035      statvalue  = "TENTATIVE"           ;Indicates event is
5036                                         ;tentative.
5037                 / "CONFIRMED"           ;Indicates event is
5038                                         ;definite.
5039                 / "CANCELLED"           ;Indicates event was
5040                                         ;cancelled.
5041         ;Status values for a "VEVENT"
5042
5043
5044
5045 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 88]</span>
5046 </pre><pre class="newpage"><a name="page-89" id="page-89" href="#page-89" class="invisible"> </a>
5047 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5048
5049
5050      statvalue  =/ "NEEDS-ACTION"       ;Indicates to-do needs action.
5051                 / "COMPLETED"           ;Indicates to-do completed.
5052                 / "IN-PROCESS"          ;Indicates to-do in process of
5053                 / "CANCELLED"           ;Indicates to-do was cancelled.
5054         ;Status values for "VTODO".
5055
5056      statvalue  =/ "DRAFT"              ;Indicates journal is draft.
5057                 / "FINAL"               ;Indicates journal is final.
5058                 / "CANCELLED"           ;Indicates journal is removed.
5059         ;Status values for "VJOURNAL".
5060
5061    Example: The following is an example of this property for a "VEVENT"
5062    calendar component:
5063
5064      STATUS:TENTATIVE
5065
5066    The following is an example of this property for a "VTODO" calendar
5067    component:
5068
5069      STATUS:NEEDS-ACTION
5070
5071    The following is an example of this property for a "VJOURNAL"
5072    calendar component:
5073
5074      STATUS:DRAFT
5075
5076 <span class="h5"><h5><a name="section-4.8.1.12">4.8.1.12</a> Summary</h5></span>
5077
5078    Property Name: SUMMARY
5079
5080    Purpose: This property defines a short summary or subject for the
5081    calendar component.
5082
5083    Value Type: TEXT
5084
5085    Property Parameters: Non-standard, alternate text representation and
5086    language property parameters can be specified on this property.
5087
5088    Conformance: The property can be specified in "VEVENT", "VTODO",
5089    "VJOURNAL" or "VALARM" calendar components.
5090
5091    Description: This property is used in the "VEVENT", "VTODO" and
5092    "VJOURNAL" calendar components to capture a short, one line summary
5093    about the activity or journal entry.
5094
5095    This property is used in the "VALARM" calendar component to capture
5096    the subject of an EMAIL category of alarm.
5097
5098
5099
5100
5101 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 89]</span>
5102 </pre><pre class="newpage"><a name="page-90" id="page-90" href="#page-90" class="invisible"> </a>
5103 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5104
5105
5106    Format Definition: The property is defined by the following notation:
5107
5108      summary    = "SUMMARY" summparam ":" text CRLF
5109
5110      summparam  = *(
5111
5112                 ; the following are optional,
5113                 ; but MUST NOT occur more than once
5114
5115                 (";" altrepparam) / (";" languageparam) /
5116
5117                 ; the following is optional,
5118                 ; and MAY occur more than once
5119
5120                 (";" xparam)
5121
5122                 )
5123
5124    Example: The following is an example of this property:
5125
5126      SUMMARY:Department Party
5127
5128 <span class="h4"><h4><a name="section-4.8.2">4.8.2</a> Date and Time Component Properties</h4></span>
5129
5130    The following properties specify date and time related information in
5131    calendar components.
5132
5133 <span class="h5"><h5><a name="section-4.8.2.1">4.8.2.1</a> Date/Time Completed</h5></span>
5134
5135    Property Name: COMPLETED
5136
5137    Purpose: This property defines the date and time that a to-do was
5138    actually completed.
5139
5140    Value Type: DATE-TIME
5141
5142    Property Parameters: Non-standard property parameters can be
5143    specified on this property.
5144
5145    Conformance: The property can be specified in a "VTODO" calendar
5146    component.
5147
5148    Description: The date and time MUST be in a UTC format.
5149
5150    Format Definition: The property is defined by the following notation:
5151
5152      completed  = "COMPLETED" compparam ":" date-time CRLF
5153
5154
5155
5156
5157 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 90]</span>
5158 </pre><pre class="newpage"><a name="page-91" id="page-91" href="#page-91" class="invisible"> </a>
5159 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5160
5161
5162      compparam  = *(";" xparam)
5163
5164    Example: The following is an example of this property:
5165
5166      COMPLETED:19960401T235959Z
5167
5168 <span class="h5"><h5><a name="section-4.8.2.2">4.8.2.2</a> Date/Time End</h5></span>
5169
5170    Property Name: DTEND
5171
5172    Purpose: This property specifies the date and time that a calendar
5173    component ends.
5174
5175    Value Type: The default value type is DATE-TIME. The value type can
5176    be set to a DATE value type.
5177
5178    Property Parameters: Non-standard, value data type, time zone
5179    identifier property parameters can be specified on this property.
5180
5181    Conformance: This property can be specified in "VEVENT" or
5182    "VFREEBUSY" calendar components.
5183
5184    Description: Within the "VEVENT" calendar component, this property
5185    defines the date and time by which the event ends. The value MUST be
5186    later in time than the value of the "DTSTART" property.
5187
5188    Within the "VFREEBUSY" calendar component, this property defines the
5189    end date and time for the free or busy time information. The time
5190    MUST be specified in the UTC time format. The value MUST be later in
5191    time than the value of the "DTSTART" property.
5192
5193    Format Definition: The property is defined by the following notation:
5194
5195      dtend      = "DTEND" dtendparam":" dtendval CRLF
5196
5197      dtendparam = *(
5198
5199                 ; the following are optional,
5200                 ; but MUST NOT occur more than once
5201
5202                 (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
5203                 (";" tzidparam) /
5204
5205                 ; the following is optional,
5206                 ; and MAY occur more than once
5207
5208
5209
5210
5211
5212
5213 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 91]</span>
5214 </pre><pre class="newpage"><a name="page-92" id="page-92" href="#page-92" class="invisible"> </a>
5215 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5216
5217
5218                 (";" xparam)
5219
5220                 )
5221
5222
5223
5224      dtendval   = date-time / date
5225      ;Value MUST match value type
5226
5227    Example: The following is an example of this property:
5228
5229      DTEND:19960401T235959Z
5230
5231      DTEND;VALUE=DATE:19980704
5232
5233 <span class="h5"><h5><a name="section-4.8.2.3">4.8.2.3</a> Date/Time Due</h5></span>
5234
5235    Property Name: DUE
5236
5237    Purpose: This property defines the date and time that a to-do is
5238    expected to be completed.
5239
5240    Value Type: The default value type is DATE-TIME. The value type can
5241    be set to a DATE value type.
5242
5243    Property Parameters: Non-standard, value data type, time zone
5244    identifier property parameters can be specified on this property.
5245
5246    Conformance: The property can be specified once in a "VTODO" calendar
5247    component.
5248
5249    Description: The value MUST be a date/time equal to or after the
5250    DTSTART value, if specified.
5251
5252    Format Definition: The property is defined by the following notation:
5253
5254      due        = "DUE" dueparam":" dueval CRLF
5255
5256      dueparam   = *(
5257                 ; the following are optional,
5258                 ; but MUST NOT occur more than once
5259
5260                 (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
5261                 (";" tzidparam) /
5262
5263                 ; the following is optional,
5264                 ; and MAY occur more than once
5265
5266
5267
5268
5269 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 92]</span>
5270 </pre><pre class="newpage"><a name="page-93" id="page-93" href="#page-93" class="invisible"> </a>
5271 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5272
5273
5274                   *(";" xparam)
5275
5276                 )
5277
5278
5279
5280      dueval     = date-time / date
5281      ;Value MUST match value type
5282
5283    Example: The following is an example of this property:
5284
5285      DUE:19980430T235959Z
5286
5287 <span class="h5"><h5><a name="section-4.8.2.4">4.8.2.4</a> Date/Time Start</h5></span>
5288
5289    Property Name: DTSTART
5290
5291    Purpose: This property specifies when the calendar component begins.
5292
5293    Value Type: The default value type is DATE-TIME. The time value MUST
5294    be one of the forms defined for the DATE-TIME value type. The value
5295    type can be set to a DATE value type.
5296
5297    Property Parameters: Non-standard, value data type, time zone
5298    identifier property parameters can be specified on this property.
5299
5300    Conformance: This property can be specified in the "VEVENT", "VTODO",
5301    "VFREEBUSY", or "VTIMEZONE" calendar components.
5302
5303    Description: Within the "VEVENT" calendar component, this property
5304    defines the start date and time for the event. The property is
5305    REQUIRED in "VEVENT" calendar components. Events can have a start
5306    date/time but no end date/time. In that case, the event does not take
5307    up any time.
5308
5309    Within the "VFREEBUSY" calendar component, this property defines the
5310    start date and time for the free or busy time information. The time
5311    MUST be specified in UTC time.
5312
5313    Within the "VTIMEZONE" calendar component, this property defines the
5314    effective start date and time for a time zone specification. This
5315    property is REQUIRED within each STANDARD and DAYLIGHT part included
5316    in "VTIMEZONE" calendar components and MUST be specified as a local
5317    DATE-TIME without the "TZID" property parameter.
5318
5319    Format Definition: The property is defined by the following notation:
5320
5321      dtstart    = "DTSTART" dtstparam ":" dtstval CRLF
5322
5323
5324
5325 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 93]</span>
5326 </pre><pre class="newpage"><a name="page-94" id="page-94" href="#page-94" class="invisible"> </a>
5327 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5328
5329
5330      dtstparam  = *(
5331
5332                 ; the following are optional,
5333                 ; but MUST NOT occur more than once
5334
5335                 (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
5336                 (";" tzidparam) /
5337
5338                 ; the following is optional,
5339                 ; and MAY occur more than once
5340
5341                   *(";" xparam)
5342
5343                 )
5344
5345
5346
5347      dtstval    = date-time / date
5348      ;Value MUST match value type
5349
5350    Example: The following is an example of this property:
5351
5352      DTSTART:19980118T073000Z
5353
5354 <span class="h5"><h5><a name="section-4.8.2.5">4.8.2.5</a> Duration</h5></span>
5355
5356    Property Name: DURATION
5357
5358    Purpose: The property specifies a positive duration of time.
5359
5360    Value Type: DURATION
5361
5362    Property Parameters: Non-standard property parameters can be
5363    specified on this property.
5364
5365    Conformance: The property can be specified in "VEVENT", "VTODO",
5366    "VFREEBUSY" or "VALARM" calendar components.
5367
5368    Description: In a "VEVENT" calendar component the property may be
5369    used to specify a duration of the event, instead of an explicit end
5370    date/time. In a "VTODO" calendar component the property may be used
5371    to specify a duration for the to-do, instead of an explicit due
5372    date/time. In a "VFREEBUSY" calendar component the property may be
5373    used to specify the interval of free time being requested. In a
5374    "VALARM" calendar component the property may be used to specify the
5375    delay period prior to repeating an alarm.
5376
5377    Format Definition: The property is defined by the following notation:
5378
5379
5380
5381 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 94]</span>
5382 </pre><pre class="newpage"><a name="page-95" id="page-95" href="#page-95" class="invisible"> </a>
5383 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5384
5385
5386      duration   = "DURATION" durparam ":" dur-value CRLF
5387                   ;consisting of a positive duration of time.
5388
5389      durparam   = *(";" xparam)
5390
5391    Example: The following is an example of this property that specifies
5392    an interval of time of 1 hour and zero minutes and zero seconds:
5393
5394      DURATION:PT1H0M0S
5395
5396    The following is an example of this property that specifies an
5397    interval of time of 15 minutes.
5398
5399      DURATION:PT15M
5400
5401 <span class="h5"><h5><a name="section-4.8.2.6">4.8.2.6</a> Free/Busy Time</h5></span>
5402
5403    Property Name: FREEBUSY
5404
5405    Purpose: The property defines one or more free or busy time
5406    intervals.
5407
5408    Value Type: PERIOD. The date and time values MUST be in an UTC time
5409    format.
5410
5411    Property Parameters: Non-standard or free/busy time type property
5412    parameters can be specified on this property.
5413
5414    Conformance: The property can be specified in a "VFREEBUSY" calendar
5415    component.
5416
5417    Property Parameter: "FBTYPE" and non-standard parameters can be
5418    specified on this property.
5419
5420    Description: These time periods can be specified as either a start
5421    and end date-time or a start date-time and duration. The date and
5422    time MUST be a UTC time format.
5423
5424    "FREEBUSY" properties within the "VFREEBUSY" calendar component
5425    SHOULD be sorted in ascending order, based on start time and then end
5426    time, with the earliest periods first.
5427
5428    The "FREEBUSY" property can specify more than one value, separated by
5429    the COMMA character (US-ASCII decimal 44). In such cases, the
5430    "FREEBUSY" property values SHOULD all be of the same "FBTYPE"
5431    property parameter type (e.g., all values of a particular "FBTYPE"
5432    listed together in a single property).
5433
5434
5435
5436
5437 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 95]</span>
5438 </pre><pre class="newpage"><a name="page-96" id="page-96" href="#page-96" class="invisible"> </a>
5439 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5440
5441
5442    Format Definition: The property is defined by the following notation:
5443
5444      freebusy   = "FREEBUSY" fbparam ":" fbvalue
5445                   CRLF
5446
5447      fbparam    = *(
5448                 ; the following is optional,
5449                 ; but MUST NOT occur more than once
5450
5451                 (";" fbtypeparam) /
5452
5453                 ; the following is optional,
5454                 ; and MAY occur more than once
5455
5456                 (";" xparam)
5457
5458                 )
5459
5460      fbvalue    = period *["," period]
5461      ;Time value MUST be in the UTC time format.
5462
5463    Example: The following are some examples of this property:
5464
5465      FREEBUSY;FBTYPE=BUSY-UNAVAILABLE:19970308T160000Z/PT8H30M
5466
5467      FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H
5468
5469      FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H,
5470       19970308T230000Z/19970309T000000Z
5471
5472 <span class="h5"><h5><a name="section-4.8.2.7">4.8.2.7</a> Time Transparency</h5></span>
5473
5474    Property Name: TRANSP
5475
5476    Purpose: This property defines whether an event is transparent or not
5477    to busy time searches.
5478
5479    Value Type: TEXT
5480
5481    Property Parameters: Non-standard property parameters can be
5482    specified on this property.
5483
5484    Conformance: This property can be specified once in a "VEVENT"
5485    calendar component.
5486
5487    Description: Time Transparency is the characteristic of an event that
5488    determines whether it appears to consume time on a calendar. Events
5489    that consume actual time for the individual or resource associated
5490
5491
5492
5493 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 96]</span>
5494 </pre><pre class="newpage"><a name="page-97" id="page-97" href="#page-97" class="invisible"> </a>
5495 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5496
5497
5498    with the calendar SHOULD be recorded as OPAQUE, allowing them to be
5499    detected by free-busy time searches. Other events, which do not take
5500    up the individual's (or resource's) time SHOULD be recorded as
5501    TRANSPARENT, making them invisible to free-busy time searches.
5502
5503    Format Definition: The property is specified by the following
5504    notation:
5505
5506      transp     = "TRANSP" tranparam ":" transvalue CRLF
5507
5508      tranparam  = *(";" xparam)
5509
5510      transvalue = "OPAQUE"      ;Blocks or opaque on busy time searches.
5511                 / "TRANSPARENT" ;Transparent on busy time searches.
5512         ;Default value is OPAQUE
5513
5514    Example: The following is an example of this property for an event
5515    that is transparent or does not block on free/busy time searches:
5516
5517      TRANSP:TRANSPARENT
5518
5519    The following is an example of this property for an event that is
5520    opaque or blocks on free/busy time searches:
5521
5522      TRANSP:OPAQUE
5523
5524 <span class="h4"><h4><a name="section-4.8.3">4.8.3</a> Time Zone Component Properties</h4></span>
5525
5526    The following properties specify time zone information in calendar
5527    components.
5528
5529 <span class="h5"><h5><a name="section-4.8.3.1">4.8.3.1</a> Time Zone Identifier</h5></span>
5530
5531    Property Name: TZID
5532
5533    Purpose: This property specifies the text value that uniquely
5534    identifies the "VTIMEZONE" calendar component.
5535
5536    Value Type: TEXT
5537
5538    Property Parameters: Non-standard property parameters can be
5539    specified on this property.
5540
5541    Conformance: This property MUST be specified in a "VTIMEZONE"
5542    calendar component.
5543
5544
5545
5546
5547
5548
5549 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 97]</span>
5550 </pre><pre class="newpage"><a name="page-98" id="page-98" href="#page-98" class="invisible"> </a>
5551 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5552
5553
5554    Description: This is the label by which a time zone calendar
5555    component is referenced by any iCalendar properties whose data type
5556    is either DATE-TIME or TIME and not intended to specify a UTC or a
5557    "floating" time. The presence of the SOLIDUS character (US-ASCII
5558    decimal 47) as a prefix, indicates that this TZID represents an
5559    unique ID in a globally defined time zone registry (when such
5560    registry is defined).
5561
5562         Note: This document does not define a naming convention for time
5563         zone identifiers. Implementers may want to use the naming
5564         conventions defined in existing time zone specifications such as
5565         the public-domain Olson database [<a href="#ref-TZ" title="&quot;ftp://elsie.nci.nih.gov/pub/&quot;">TZ</a>]. The specification of
5566         globally unique time zone identifiers is not addressed by this
5567         document and is left for future study.
5568
5569    Format Definition: This property is defined by the following
5570    notation:
5571
5572      tzid       = "TZID" tzidpropparam ":" [<a href="#ref-tzidprefix">tzidprefix</a>] text CRLF
5573
5574      tzidpropparam      = *(";" xparam)
5575
5576      ;tzidprefix        = "/"
5577      ; Defined previously. Just listed here for reader convenience.
5578
5579    Example: The following are examples of non-globally unique time zone
5580    identifiers:
5581
5582      TZID:US-Eastern
5583
5584      TZID:California-Los_Angeles
5585
5586    The following is an example of a fictitious globally unique time zone
5587    identifier:
5588
5589      TZID:/US-New_York-New_York
5590
5591 <span class="h5"><h5><a name="section-4.8.3.2">4.8.3.2</a> Time Zone Name</h5></span>
5592
5593    Property Name: TZNAME
5594
5595    Purpose: This property specifies the customary designation for a time
5596    zone description.
5597
5598    Value Type: TEXT
5599
5600    Property Parameters: Non-standard and language property parameters
5601    can be specified on this property.
5602
5603
5604
5605 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 98]</span>
5606 </pre><pre class="newpage"><a name="page-99" id="page-99" href="#page-99" class="invisible"> </a>
5607 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5608
5609
5610    Conformance: This property can be specified in a "VTIMEZONE" calendar
5611    component.
5612
5613    Description: This property may be specified in multiple languages; in
5614    order to provide for different language requirements.
5615
5616    Format Definition: This property is defined by the following
5617    notation:
5618
5619      tzname     = "TZNAME" tznparam ":" text CRLF
5620
5621      tznparam   = *(
5622
5623                 ; the following is optional,
5624                 ; but MUST NOT occur more than once
5625
5626                 (";" languageparam) /
5627
5628                 ; the following is optional,
5629                 ; and MAY occur more than once
5630
5631                 (";" xparam)
5632
5633                 )
5634
5635    Example: The following are example of this property:
5636
5637      TZNAME:EST
5638
5639    The following is an example of this property when two different
5640    languages for the time zone name are specified:
5641
5642      TZNAME;LANGUAGE=en:EST
5643      TZNAME;LANGUAGE=fr-CA:HNE
5644
5645 <span class="h5"><h5><a name="section-4.8.3.3">4.8.3.3</a> Time Zone Offset From</h5></span>
5646
5647    Property Name: TZOFFSETFROM
5648
5649    Purpose: This property specifies the offset which is in use prior to
5650    this time zone observance.
5651
5652    Value Type: UTC-OFFSET
5653
5654    Property Parameters: Non-standard property parameters can be
5655    specified on this property.
5656
5657
5658
5659
5660
5661 <span class="grey">Dawson &amp; Stenerson          Standards Track                    [Page 99]</span>
5662 </pre><pre class="newpage"><a name="page-100" id="page-100" href="#page-100" class="invisible"> </a>
5663 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5664
5665
5666    Conformance: This property MUST be specified in a "VTIMEZONE"
5667    calendar component.
5668
5669    Description: This property specifies the offset which is in use prior
5670    to this time observance. It is used to calculate the absolute time at
5671    which the transition to a given observance takes place. This property
5672    MUST only be specified in a "VTIMEZONE" calendar component. A
5673    "VTIMEZONE" calendar component MUST include this property. The
5674    property value is a signed numeric indicating the number of hours and
5675    possibly minutes from UTC. Positive numbers represent time zones east
5676    of the prime meridian, or ahead of UTC. Negative numbers represent
5677    time zones west of the prime meridian, or behind UTC.
5678
5679    Format Definition: The property is defined by the following notation:
5680
5681      tzoffsetfrom       = "TZOFFSETFROM" frmparam ":" utc-offset
5682                           CRLF
5683
5684      frmparam   = *(";" xparam)
5685
5686    Example: The following are examples of this property:
5687
5688      TZOFFSETFROM:-0500
5689
5690      TZOFFSETFROM:+1345
5691
5692 <span class="h5"><h5><a name="section-4.8.3.4">4.8.3.4</a> Time Zone Offset To</h5></span>
5693
5694    Property Name: TZOFFSETTO
5695
5696    Purpose: This property specifies the offset which is in use in this
5697    time zone observance.
5698
5699    Value Type: UTC-OFFSET
5700
5701    Property Parameters: Non-standard property parameters can be
5702    specified on this property.
5703
5704    Conformance: This property MUST be specified in a "VTIMEZONE"
5705    calendar component.
5706
5707    Description: This property specifies the offset which is in use in
5708    this time zone observance. It is used to calculate the absolute time
5709    for the new observance. The property value is a signed numeric
5710    indicating the number of hours and possibly minutes from UTC.
5711    Positive numbers represent time zones east of the prime meridian, or
5712    ahead of UTC. Negative numbers represent time zones west of the prime
5713    meridian, or behind UTC.
5714
5715
5716
5717 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 100]</span>
5718 </pre><pre class="newpage"><a name="page-101" id="page-101" href="#page-101" class="invisible"> </a>
5719 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5720
5721
5722    Format Definition: The property is defined by the following notation:
5723
5724      tzoffsetto = "TZOFFSETTO" toparam ":" utc-offset CRLF
5725
5726      toparam    = *(";" xparam)
5727
5728    Example: The following are examples of this property:
5729
5730      TZOFFSETTO:-0400
5731
5732      TZOFFSETTO:+1245
5733
5734 <span class="h5"><h5><a name="section-4.8.3.5">4.8.3.5</a> Time Zone URL</h5></span>
5735
5736    Property Name: TZURL
5737
5738    Purpose: The TZURL provides a means for a VTIMEZONE component to
5739    point to a network location that can be used to retrieve an up-to-
5740    date version of itself.
5741
5742    Value Type: URI
5743
5744    Property Parameters: Non-standard property parameters can be
5745    specified on this property.
5746
5747    Conformance: This property can be specified in a "VTIMEZONE" calendar
5748    component.
5749
5750    Description: The TZURL provides a means for a VTIMEZONE component to
5751    point to a network location that can be used to retrieve an up-to-
5752    date version of itself. This provides a hook to handle changes
5753    government bodies impose upon time zone definitions. Retrieval of
5754    this resource results in an iCalendar object containing a single
5755    VTIMEZONE component and a METHOD property set to PUBLISH.
5756
5757    Format Definition: The property is defined by the following notation:
5758
5759      tzurl      = "TZURL" tzurlparam ":" uri CRLF
5760
5761      tzurlparam = *(";" xparam)
5762
5763    Example: The following is an example of this property:
5764
5765      TZURL:http://timezones.r.us.net/tz/US-California-Los_Angeles
5766
5767
5768
5769
5770
5771
5772
5773 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 101]</span>
5774 </pre><pre class="newpage"><a name="page-102" id="page-102" href="#page-102" class="invisible"> </a>
5775 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5776
5777
5778 <span class="h4"><h4><a name="section-4.8.4">4.8.4</a> Relationship Component Properties</h4></span>
5779
5780    The following properties specify relationship information in calendar
5781    components.
5782
5783 <span class="h5"><h5><a name="section-4.8.4.1">4.8.4.1</a> Attendee</h5></span>
5784
5785    Property Name: ATTENDEE
5786
5787    Purpose: The property defines an "Attendee" within a calendar
5788    component.
5789
5790    Value Type: CAL-ADDRESS
5791
5792    Property Parameters: Non-standard, language, calendar user type,
5793    group or list membership, participation role, participation status,
5794    RSVP expectation, delegatee, delegator, sent by, common name or
5795    directory entry reference property parameters can be specified on
5796    this property.
5797
5798    Conformance: This property MUST be specified in an iCalendar object
5799    that specifies a group scheduled calendar entity. This property MUST
5800    NOT be specified in an iCalendar object when publishing the calendar
5801    information (e.g., NOT in an iCalendar object that specifies the
5802    publication of a calendar user's busy time, event, to-do or journal).
5803    This property is not specified in an iCalendar object that specifies
5804    only a time zone definition or that defines calendar entities that
5805    are not group scheduled entities, but are entities only on a single
5806    user's calendar.
5807
5808    Description: The property MUST only be specified within calendar
5809    components to specify participants, non-participants and the chair of
5810    a group scheduled calendar entity. The property is specified within
5811    an "EMAIL" category of the "VALARM" calendar component to specify an
5812    email address that is to receive the email type of iCalendar alarm.
5813
5814    The property parameter CN is for the common or displayable name
5815    associated with the calendar address; ROLE, for the intended role
5816    that the attendee will have in the calendar component; PARTSTAT, for
5817    the status of the attendee's participation; RSVP, for indicating
5818    whether the favor of a reply is requested; CUTYPE, to indicate the
5819    type of calendar user; MEMBER, to indicate the groups that the
5820    attendee belongs to; DELEGATED-TO, to indicate the calendar users
5821    that the original request was delegated to; and DELEGATED-FROM, to
5822    indicate whom the request was delegated from; SENT-BY, to indicate
5823    whom is acting on behalf of the ATTENDEE; and DIR, to indicate the
5824    URI that points to the directory information corresponding to the
5825    attendee. These property parameters can be specified on an "ATTENDEE"
5826
5827
5828
5829 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 102]</span>
5830 </pre><pre class="newpage"><a name="page-103" id="page-103" href="#page-103" class="invisible"> </a>
5831 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5832
5833
5834    property in either a "VEVENT", "VTODO" or "VJOURNAL" calendar
5835    component. They MUST not be specified in an "ATTENDEE" property in a
5836    "VFREEBUSY" or "VALARM" calendar component. If the LANGUAGE property
5837    parameter is specified, the identified language applies to the CN
5838    parameter.
5839
5840    A recipient delegated a request MUST inherit the RSVP and ROLE values
5841    from the attendee that delegated the request to them.
5842
5843    Multiple attendees can be specified by including multiple "ATTENDEE"
5844    properties within the calendar component.
5845
5846    Format Definition: The property is defined by the following notation:
5847
5848      attendee   = "ATTENDEE" attparam ":" cal-address CRLF
5849
5850      attparam   = *(
5851
5852                 ; the following are optional,
5853                 ; but MUST NOT occur more than once
5854
5855                 (";" cutypeparam) / (";"memberparam) /
5856                 (";" roleparam) / (";" partstatparam) /
5857                 (";" rsvpparam) / (";" deltoparam) /
5858                 (";" delfromparam) / (";" sentbyparam) /
5859                 (";"cnparam) / (";" dirparam) /
5860                 (";" languageparam) /
5861
5862                 ; the following is optional,
5863                 ; and MAY occur more than once
5864
5865                 (";" xparam)
5866
5867                 )
5868
5869    Example: The following are examples of this property's use for a to-
5870    do:
5871
5872      ORGANIZER:MAILTO:jsmith@host1.com
5873      ATTENDEE;MEMBER="MAILTO:DEV-GROUP@host2.com":
5874       MAILTO:joecool@host2.com
5875      ATTENDEE;DELEGATED-FROM="MAILTO:immud@host3.com":
5876       MAILTO:ildoit@host1.com
5877
5878    The following is an example of this property used for specifying
5879    multiple attendees to an event:
5880
5881
5882
5883
5884
5885 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 103]</span>
5886 </pre><pre class="newpage"><a name="page-104" id="page-104" href="#page-104" class="invisible"> </a>
5887 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5888
5889
5890      ORGANIZER:MAILTO:jsmith@host1.com
5891      ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;CN=Henry Cabot
5892       :MAILTO:hcabot@host2.com
5893      ATTENDEE;ROLE=REQ-PARTICIPANT;DELEGATED-FROM="MAILTO:bob@host.com"
5894       ;PARTSTAT=ACCEPTED;CN=Jane Doe:MAILTO:jdoe@host1.com
5895
5896    The following is an example of this property with a URI to the
5897    directory information associated with the attendee:
5898
5899      ATTENDEE;CN=John Smith;DIR="ldap://host.com:6666/o=eDABC%
5900       20Industries,c=3DUS??(cn=3DBJim%20Dolittle)":MAILTO:jimdo@
5901       host1.com
5902
5903    The following is an example of this property with "delegatee" and
5904    "delegator" information for an event:
5905
5906      ORGANIZER;CN=John Smith:MAILTO:jsmith@host.com
5907      ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;DELEGATED-FROM=
5908       "MAILTO:iamboss@host2.com";CN=Henry Cabot:MAILTO:hcabot@
5909       host2.com
5910      ATTENDEE;ROLE=NON-PARTICIPANT;PARTSTAT=DELEGATED;DELEGATED-TO=
5911       "MAILTO:hcabot@host2.com";CN=The Big Cheese:MAILTO:iamboss
5912       @host2.com
5913      ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=ACCEPTED;CN=Jane Doe
5914       :MAILTO:jdoe@host1.com
5915
5916    Example: The following is an example of this property's use when
5917    another calendar user is acting on behalf of the "Attendee":
5918
5919      ATTENDEE;SENT-BY=MAILTO:jan_doe@host1.com;CN=John Smith:MAILTO:
5920       jsmith@host1.com
5921
5922 <span class="h5"><h5><a name="section-4.8.4.2">4.8.4.2</a> Contact</h5></span>
5923
5924    Property Name: CONTACT
5925
5926    Purpose: The property is used to represent contact information or
5927    alternately a reference to contact information associated with the
5928    calendar component.
5929
5930    Value Type: TEXT
5931
5932    Property Parameters: Non-standard, alternate text representation and
5933    language property parameters can be specified on this property.
5934
5935    Conformance: The property can be specified in a "VEVENT", "VTODO",
5936    "VJOURNAL" or "VFREEBUSY" calendar component.
5937
5938
5939
5940
5941 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 104]</span>
5942 </pre><pre class="newpage"><a name="page-105" id="page-105" href="#page-105" class="invisible"> </a>
5943 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
5944
5945
5946    Description: The property value consists of textual contact
5947    information. An alternative representation for the property value can
5948    also be specified that refers to a URI pointing to an alternate form,
5949    such as a vCard [<a href="http://tools.ietf.org/html/rfc2426" title="&quot;vCard MIME Directory Profile&quot;">RFC 2426</a>], for the contact information.
5950
5951    Format Definition: The property is defined by the following notation:
5952
5953      contact    = "CONTACT" contparam ":" text CRLF
5954
5955      contparam  = *(
5956                 ; the following are optional,
5957                 ; but MUST NOT occur more than once
5958
5959                 (";" altrepparam) / (";" languageparam) /
5960
5961                 ; the following is optional,
5962                 ; and MAY occur more than once
5963
5964                 (";" xparam)
5965
5966                 )
5967
5968    Example: The following is an example of this property referencing
5969    textual contact information:
5970
5971      CONTACT:Jim Dolittle\, ABC Industries\, +1-919-555-1234
5972
5973    The following is an example of this property with an alternate
5974    representation of a LDAP URI to a directory entry containing the
5975    contact information:
5976
5977      CONTACT;ALTREP="ldap://host.com:6666/o=3DABC%20Industries\,
5978       c=3DUS??(cn=3DBJim%20Dolittle)":Jim Dolittle\, ABC Industries\,
5979       +1-919-555-1234
5980
5981    The following is an example of this property with an alternate
5982    representation of a MIME body part containing the contact
5983    information, such as a vCard [<a href="http://tools.ietf.org/html/rfc2426" title="&quot;vCard MIME Directory Profile&quot;">RFC 2426</a>] embedded in a [<a href="#ref-MIME-DIR">MIME-DIR</a>]
5984    content-type:
5985
5986      CONTACT;ALTREP="CID=&lt;part3.msg970930T083000SILVER@host.com&gt;":Jim
5987        Dolittle\, ABC Industries\, +1-919-555-1234
5988
5989    The following is an example of this property referencing a network
5990    resource, such as a vCard [<a href="http://tools.ietf.org/html/rfc2426" title="&quot;vCard MIME Directory Profile&quot;">RFC 2426</a>] object containing the contact
5991    information:
5992
5993
5994
5995
5996
5997 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 105]</span>
5998 </pre><pre class="newpage"><a name="page-106" id="page-106" href="#page-106" class="invisible"> </a>
5999 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6000
6001
6002      CONTACT;ALTREP="http://host.com/pdi/jdoe.vcf":Jim
6003        Dolittle\, ABC Industries\, +1-919-555-1234
6004
6005 <span class="h5"><h5><a name="section-4.8.4.3">4.8.4.3</a> Organizer</h5></span>
6006
6007    Property Name: ORGANIZER
6008
6009    Purpose: The property defines the organizer for a calendar component.
6010
6011    Value Type: CAL-ADDRESS
6012
6013    Property Parameters: Non-standard, language, common name, directory
6014    entry reference, sent by property parameters can be specified on this
6015    property.
6016
6017    Conformance: This property MUST be specified in an iCalendar object
6018    that specifies a group scheduled calendar entity. This property MUST
6019    be specified in an iCalendar object that specifies the publication of
6020    a calendar user's busy time. This property MUST NOT be specified in
6021    an iCalendar object that specifies only a time zone definition or
6022    that defines calendar entities that are not group scheduled entities,
6023    but are entities only on a single user's calendar.
6024
6025    Description: The property is specified within the "VEVENT", "VTODO",
6026    "VJOURNAL calendar components to specify the organizer of a group
6027    scheduled calendar entity. The property is specified within the
6028    "VFREEBUSY" calendar component to specify the calendar user
6029    requesting the free or busy time. When publishing a "VFREEBUSY"
6030    calendar component, the property is used to specify the calendar that
6031    the published busy time came from.
6032
6033    The property has the property parameters CN, for specifying the
6034    common or display name associated with the "Organizer", DIR, for
6035    specifying a pointer to the directory information associated with the
6036    "Organizer", SENT-BY, for specifying another calendar user that is
6037    acting on behalf of the "Organizer". The non-standard parameters may
6038    also be specified on this property. If the LANGUAGE property
6039    parameter is specified, the identified language applies to the CN
6040    parameter value.
6041
6042    Format Definition: The property is defined by the following notation:
6043
6044      organizer  = "ORGANIZER" orgparam ":"
6045                   cal-address CRLF
6046
6047      orgparam   = *(
6048
6049                 ; the following are optional,
6050
6051
6052
6053 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 106]</span>
6054 </pre><pre class="newpage"><a name="page-107" id="page-107" href="#page-107" class="invisible"> </a>
6055 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6056
6057
6058                 ; but MUST NOT occur more than once
6059
6060                 (";" cnparam) / (";" dirparam) / (";" sentbyparam) /
6061                 (";" languageparam) /
6062
6063                 ; the following is optional,
6064                 ; and MAY occur more than once
6065
6066                 (";" xparam)
6067
6068                 )
6069
6070    Example: The following is an example of this property:
6071
6072      ORGANIZER;CN=John Smith:MAILTO:jsmith@host1.com
6073
6074    The following is an example of this property with a pointer to the
6075    directory information associated with the organizer:
6076
6077      ORGANIZER;CN=JohnSmith;DIR="ldap://host.com:6666/o=3DDC%20Associ
6078       ates,c=3DUS??(cn=3DJohn%20Smith)":MAILTO:jsmith@host1.com
6079
6080    The following is an example of this property used by another calendar
6081    user who is acting on behalf of the organizer, with responses
6082    intended to be sent back to the organizer, not the other calendar
6083    user:
6084
6085      ORGANIZER;SENT-BY="MAILTO:jane_doe@host.com":
6086       MAILTO:jsmith@host1.com
6087
6088 <span class="h5"><h5><a name="section-4.8.4.4">4.8.4.4</a> Recurrence ID</h5></span>
6089
6090    Property Name: RECURRENCE-ID
6091
6092    Purpose: This property is used in conjunction with the "UID" and
6093    "SEQUENCE" property to identify a specific instance of a recurring
6094    "VEVENT", "VTODO" or "VJOURNAL" calendar component. The property
6095    value is the effective value of the "DTSTART" property of the
6096    recurrence instance.
6097
6098    Value Type: The default value type for this property is DATE-TIME.
6099    The time format can be any of the valid forms defined for a DATE-TIME
6100    value type. See DATE-TIME value type definition for specific
6101    interpretations of the various forms. The value type can be set to
6102    DATE.
6103
6104
6105
6106
6107
6108
6109 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 107]</span>
6110 </pre><pre class="newpage"><a name="page-108" id="page-108" href="#page-108" class="invisible"> </a>
6111 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6112
6113
6114    Property Parameters: Non-standard property, value data type, time
6115    zone identifier and recurrence identifier range parameters can be
6116    specified on this property.
6117
6118    Conformance: This property can be specified in an iCalendar object
6119    containing a recurring calendar component.
6120
6121    Description: The full range of calendar components specified by a
6122    recurrence set is referenced by referring to just the "UID" property
6123    value corresponding to the calendar component. The "RECURRENCE-ID"
6124    property allows the reference to an individual instance within the
6125    recurrence set.
6126
6127    If the value of the "DTSTART" property is a DATE type value, then the
6128    value MUST be the calendar date for the recurrence instance.
6129
6130    The date/time value is set to the time when the original recurrence
6131    instance would occur; meaning that if the intent is to change a
6132    Friday meeting to Thursday, the date/time is still set to the
6133    original Friday meeting.
6134
6135    The "RECURRENCE-ID" property is used in conjunction with the "UID"
6136    and "SEQUENCE" property to identify a particular instance of a
6137    recurring event, to-do or journal. For a given pair of "UID" and
6138    "SEQUENCE" property values, the "RECURRENCE-ID" value for a
6139    recurrence instance is fixed. When the definition of the recurrence
6140    set for a calendar component changes, and hence the "SEQUENCE"
6141    property value changes, the "RECURRENCE-ID" for a given recurrence
6142    instance might also change.The "RANGE" parameter is used to specify
6143    the effective range of recurrence instances from the instance
6144    specified by the "RECURRENCE-ID" property value. The default value
6145    for the range parameter is the single recurrence instance only. The
6146    value can also be "THISANDPRIOR" to indicate a range defined by the
6147    given recurrence instance and all prior instances or the value can be
6148    "THISANDFUTURE" to indicate a range defined by the given recurrence
6149    instance and all subsequent instances.
6150
6151    Format Definition: The property is defined by the following notation:
6152
6153      recurid    = "RECURRENCE-ID" ridparam ":" ridval CRLF
6154
6155      ridparam   = *(
6156
6157                 ; the following are optional,
6158                 ; but MUST NOT occur more than once
6159
6160                 (";" "VALUE" "=" ("DATE-TIME" / "DATE)) /
6161                 (";" tzidparam) / (";" rangeparam) /
6162
6163
6164
6165 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 108]</span>
6166 </pre><pre class="newpage"><a name="page-109" id="page-109" href="#page-109" class="invisible"> </a>
6167 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6168
6169
6170                 ; the following is optional,
6171                 ; and MAY occur more than once
6172
6173                 (";" xparam)
6174
6175                 )
6176
6177      ridval     = date-time / date
6178      ;Value MUST match value type
6179
6180    Example: The following are examples of this property:
6181
6182      RECURRENCE-ID;VALUE=DATE:19960401
6183
6184      RECURRENCE-ID;RANGE=THISANDFUTURE:19960120T120000Z
6185
6186 <span class="h5"><h5><a name="section-4.8.4.5">4.8.4.5</a> Related To</h5></span>
6187
6188    Property Name: RELATED-TO
6189
6190    Purpose: The property is used to represent a relationship or
6191    reference between one calendar component and another.
6192
6193    Value Type: TEXT
6194
6195    Property Parameters: Non-standard and relationship type property
6196    parameters can be specified on this property.
6197
6198    Conformance: The property can be specified one or more times in the
6199    "VEVENT", "VTODO" or "VJOURNAL" calendar components.
6200
6201    Description: The property value consists of the persistent, globally
6202    unique identifier of another calendar component. This value would be
6203    represented in a calendar component by the "UID" property.
6204
6205    By default, the property value points to another calendar component
6206    that has a PARENT relationship to the referencing object. The
6207    "RELTYPE" property parameter is used to either explicitly state the
6208    default PARENT relationship type to the referenced calendar component
6209    or to override the default PARENT relationship type and specify
6210    either a CHILD or SIBLING relationship. The PARENT relationship
6211    indicates that the calendar component is a subordinate of the
6212    referenced calendar component. The CHILD relationship indicates that
6213    the calendar component is a superior of the referenced calendar
6214    component. The SIBLING relationship indicates that the calendar
6215    component is a peer of the referenced calendar component.
6216
6217
6218
6219
6220
6221 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 109]</span>
6222 </pre><pre class="newpage"><a name="page-110" id="page-110" href="#page-110" class="invisible"> </a>
6223 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6224
6225
6226    Changes to a calendar component referenced by this property can have
6227    an implicit impact on the related calendar component. For example, if
6228    a group event changes its start or end date or time, then the
6229    related, dependent events will need to have their start and end dates
6230    changed in a corresponding way. Similarly, if a PARENT calendar
6231    component is canceled or deleted, then there is an implied impact to
6232    the related CHILD calendar components. This property is intended only
6233    to provide information on the relationship of calendar components. It
6234    is up to the target calendar system to maintain any property
6235    implications of this relationship.
6236
6237    Format Definition: The property is defined by the following notation:
6238
6239      related    = "RELATED-TO" [<a href="#ref-relparam">relparam</a>] ":" text CRLF
6240
6241      relparam   = *(
6242
6243                 ; the following is optional,
6244                 ; but MUST NOT occur more than once
6245
6246                 (";" reltypeparam) /
6247
6248                 ; the following is optional,
6249                 ; and MAY occur more than once
6250
6251                 (";" xparm)
6252
6253                 )
6254
6255    The following is an example of this property:
6256
6257      RELATED-TO:&lt;jsmith.part7.19960817T083000.xyzMail@host3.com&gt;
6258
6259      RELATED-TO:&lt;19960401-080045-4000F192713-0052@host1.com&gt;
6260
6261 <span class="h5"><h5><a name="section-4.8.4.6">4.8.4.6</a> Uniform Resource Locator</h5></span>
6262
6263    Property Name: URL
6264
6265    Purpose: This property defines a Uniform Resource Locator (URL)
6266    associated with the iCalendar object.
6267
6268    Value Type: URI
6269
6270    Property Parameters: Non-standard property parameters can be
6271    specified on this property.
6272
6273
6274
6275
6276
6277 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 110]</span>
6278 </pre><pre class="newpage"><a name="page-111" id="page-111" href="#page-111" class="invisible"> </a>
6279 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6280
6281
6282    Conformance: This property can be specified once in the "VEVENT",
6283    "VTODO", "VJOURNAL" or "VFREEBUSY" calendar components.
6284
6285    Description: This property may be used in a calendar component to
6286    convey a location where a more dynamic rendition of the calendar
6287    information associated with the calendar component can be found. This
6288    memo does not attempt to standardize the form of the URI, nor the
6289    format of the resource pointed to by the property value. If the URL
6290    property and Content-Location MIME header are both specified, they
6291    MUST point to the same resource.
6292
6293    Format Definition: The property is defined by the following notation:
6294
6295      url        = "URL" urlparam ":" uri CRLF
6296
6297      urlparam   = *(";" xparam)
6298
6299    Example: The following is an example of this property:
6300
6301      URL:http://abc.com/pub/calendars/jsmith/mytime.ics
6302
6303 <span class="h5"><h5><a name="section-4.8.4.7">4.8.4.7</a> Unique Identifier</h5></span>
6304
6305    Property Name: UID
6306
6307    Purpose: This property defines the persistent, globally unique
6308    identifier for the calendar component.
6309
6310    Value Type: TEXT
6311
6312    Property Parameters: Non-standard property parameters can be
6313    specified on this property.
6314
6315    Conformance: The property MUST be specified in the "VEVENT", "VTODO",
6316    "VJOURNAL" or "VFREEBUSY" calendar components.
6317
6318    Description: The UID itself MUST be a globally unique identifier. The
6319    generator of the identifier MUST guarantee that the identifier is
6320    unique. There are several algorithms that can be used to accomplish
6321    this. The identifier is RECOMMENDED to be the identical syntax to the
6322    [<a href="http://tools.ietf.org/html/rfc822" title="&quot;Standard for the Format of ARPA Internet Text Messages&quot;">RFC 822</a>] addr-spec. A good method to assure uniqueness is to put the
6323    domain name or a domain literal IP address of the host on which the
6324    identifier was created on the right hand side of the "@", and on the
6325    left hand side, put a combination of the current calendar date and
6326    time of day (i.e., formatted in as a DATE-TIME value) along with some
6327    other currently unique (perhaps sequential) identifier available on
6328    the system (for example, a process id number). Using a date/time
6329    value on the left hand side and a domain name or domain literal on
6330
6331
6332
6333 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 111]</span>
6334 </pre><pre class="newpage"><a name="page-112" id="page-112" href="#page-112" class="invisible"> </a>
6335 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6336
6337
6338    the right hand side makes it possible to guarantee uniqueness since
6339    no two hosts should be using the same domain name or IP address at
6340    the same time. Though other algorithms will work, it is RECOMMENDED
6341    that the right hand side contain some domain identifier (either of
6342    the host itself or otherwise) such that the generator of the message
6343    identifier can guarantee the uniqueness of the left hand side within
6344    the scope of that domain.
6345
6346    This is the method for correlating scheduling messages with the
6347    referenced "VEVENT", "VTODO", or "VJOURNAL" calendar component.
6348
6349    The full range of calendar components specified by a recurrence set
6350    is referenced by referring to just the "UID" property value
6351    corresponding to the calendar component. The "RECURRENCE-ID" property
6352    allows the reference to an individual instance within the recurrence
6353    set.
6354
6355    This property is an important method for group scheduling
6356    applications to match requests with later replies, modifications or
6357    deletion requests. Calendaring and scheduling applications MUST
6358    generate this property in "VEVENT", "VTODO" and "VJOURNAL" calendar
6359    components to assure interoperability with other group scheduling
6360    applications. This identifier is created by the calendar system that
6361    generates an iCalendar object.
6362
6363    Implementations MUST be able to receive and persist values of at
6364    least 255 characters for this property.
6365
6366    Format Definition: The property is defined by the following notation:
6367
6368      uid        = "UID" uidparam ":" text CRLF
6369
6370      uidparam   = *(";" xparam)
6371
6372    Example: The following is an example of this property:
6373
6374      UID:19960401T080045Z-4000F192713-0052@host1.com
6375
6376 <span class="h4"><h4><a name="section-4.8.5">4.8.5</a> Recurrence Component Properties</h4></span>
6377
6378    The following properties specify recurrence information in calendar
6379    components.
6380
6381 <span class="h5"><h5><a name="section-4.8.5.1">4.8.5.1</a> Exception Date/Times</h5></span>
6382
6383    Property Name: EXDATE
6384
6385
6386
6387
6388
6389 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 112]</span>
6390 </pre><pre class="newpage"><a name="page-113" id="page-113" href="#page-113" class="invisible"> </a>
6391 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6392
6393
6394    Purpose: This property defines the list of date/time exceptions for a
6395    recurring calendar component.
6396
6397    Value Type: The default value type for this property is DATE-TIME.
6398    The value type can be set to DATE.
6399
6400    Property Parameters: Non-standard, value data type and time zone
6401    identifier property parameters can be specified on this property.
6402
6403    Conformance: This property can be specified in an iCalendar object
6404    that includes a recurring calendar component.
6405
6406    Description: The exception dates, if specified, are used in computing
6407    the recurrence set. The recurrence set is the complete set of
6408    recurrence instances for a calendar component. The recurrence set is
6409    generated by considering the initial "DTSTART" property along with
6410    the "RRULE", "RDATE", "EXDATE" and "EXRULE" properties contained
6411    within the iCalendar object. The "DTSTART" property defines the first
6412    instance in the recurrence set. Multiple instances of the "RRULE" and
6413    "EXRULE" properties can also be specified to define more
6414    sophisticated recurrence sets. The final recurrence set is generated
6415    by gathering all of the start date-times generated by any of the
6416    specified "RRULE" and "RDATE" properties, and then excluding any
6417    start date and times which fall within the union of start date and
6418    times generated by any specified "EXRULE" and "EXDATE" properties.
6419    This implies that start date and times within exclusion related
6420    properties (i.e., "EXDATE" and "EXRULE") take precedence over those
6421    specified by inclusion properties (i.e., "RDATE" and "RRULE"). Where
6422    duplicate instances are generated by the "RRULE" and "RDATE"
6423    properties, only one recurrence is considered. Duplicate instances
6424    are ignored.
6425
6426    The "EXDATE" property can be used to exclude the value specified in
6427    "DTSTART". However, in such cases the original "DTSTART" date MUST
6428    still be maintained by the calendaring and scheduling system because
6429    the original "DTSTART" value has inherent usage dependencies by other
6430    properties such as the "RECURRENCE-ID".
6431
6432    Format Definition: The property is defined by the following notation:
6433
6434      exdate     = "EXDATE" exdtparam ":" exdtval *("," exdtval) CRLF
6435
6436      exdtparam  = *(
6437
6438                 ; the following are optional,
6439                 ; but MUST NOT occur more than once
6440
6441                 (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
6442
6443
6444
6445 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 113]</span>
6446 </pre><pre class="newpage"><a name="page-114" id="page-114" href="#page-114" class="invisible"> </a>
6447 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6448
6449
6450                 (";" tzidparam) /
6451
6452                 ; the following is optional,
6453                 ; and MAY occur more than once
6454
6455                 (";" xparam)
6456
6457                 )
6458
6459      exdtval    = date-time / date
6460      ;Value MUST match value type
6461
6462    Example: The following is an example of this property:
6463
6464      EXDATE:19960402T010000Z,19960403T010000Z,19960404T010000Z
6465
6466 <span class="h5"><h5><a name="section-4.8.5.2">4.8.5.2</a> Exception Rule</h5></span>
6467
6468    Property Name: EXRULE
6469
6470    Purpose: This property defines a rule or repeating pattern for an
6471    exception to a recurrence set.
6472
6473    Value Type: RECUR
6474
6475    Property Parameters: Non-standard property parameters can be
6476    specified on this property.
6477
6478    Conformance: This property can be specified in "VEVENT", "VTODO" or
6479    "VJOURNAL" calendar components.
6480
6481    Description: The exception rule, if specified, is used in computing
6482    the recurrence set. The recurrence set is the complete set of
6483    recurrence instances for a calendar component. The recurrence set is
6484    generated by considering the initial "DTSTART" property along with
6485    the "RRULE", "RDATE", "EXDATE" and "EXRULE" properties contained
6486    within the iCalendar object. The "DTSTART" defines the first instance
6487    in the recurrence set. Multiple instances of the "RRULE" and "EXRULE"
6488    properties can also be specified to define more sophisticated
6489    recurrence sets. The final recurrence set is generated by gathering
6490    all of the start date-times generated by any of the specified "RRULE"
6491    and "RDATE" properties, and excluding any start date and times which
6492    fall within the union of start date and times generated by any
6493    specified "EXRULE" and "EXDATE" properties. This implies that start
6494    date and times within exclusion related properties (i.e., "EXDATE"
6495    and "EXRULE") take precedence over those specified by inclusion
6496
6497
6498
6499
6500
6501 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 114]</span>
6502 </pre><pre class="newpage"><a name="page-115" id="page-115" href="#page-115" class="invisible"> </a>
6503 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6504
6505
6506    properties (i.e., "RDATE" and "RRULE"). Where duplicate instances are
6507    generated by the "RRULE" and "RDATE" properties, only one recurrence
6508    is considered. Duplicate instances are ignored.
6509
6510    The "EXRULE" property can be used to exclude the value specified in
6511    "DTSTART". However, in such cases the original "DTSTART" date MUST
6512    still be maintained by the calendaring and scheduling system because
6513    the original "DTSTART" value has inherent usage dependencies by other
6514    properties such as the "RECURRENCE-ID".
6515
6516    Format Definition: The property is defined by the following notation:
6517
6518      exrule     = "EXRULE" exrparam ":" recur CRLF
6519
6520      exrparam   = *(";" xparam)
6521
6522    Example: The following are examples of this property. Except every
6523    other week, on Tuesday and Thursday for 4 occurrences:
6524
6525      EXRULE:FREQ=WEEKLY;COUNT=4;INTERVAL=2;BYDAY=TU,TH
6526
6527    Except daily for 10 occurrences:
6528
6529      EXRULE:FREQ=DAILY;COUNT=10
6530
6531    Except yearly in June and July for 8 occurrences:
6532
6533      EXRULE:FREQ=YEARLY;COUNT=8;BYMONTH=6,7
6534
6535 <span class="h5"><h5><a name="section-4.8.5.3">4.8.5.3</a> Recurrence Date/Times</h5></span>
6536
6537    Property Name: RDATE
6538
6539    Purpose: This property defines the list of date/times for a
6540    recurrence set.
6541
6542    Value Type: The default value type for this property is DATE-TIME.
6543    The value type can be set to DATE or PERIOD.
6544
6545    Property Parameters: Non-standard, value data type and time zone
6546    identifier property parameters can be specified on this property.
6547
6548    Conformance: The property can be specified in "VEVENT", "VTODO",
6549    "VJOURNAL" or "VTIMEZONE" calendar components.
6550
6551
6552
6553
6554
6555
6556
6557 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 115]</span>
6558 </pre><pre class="newpage"><a name="page-116" id="page-116" href="#page-116" class="invisible"> </a>
6559 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6560
6561
6562    Description: This property can appear along with the "RRULE" property
6563    to define an aggregate set of repeating occurrences. When they both
6564    appear in an iCalendar object, the recurring events are defined by
6565    the union of occurrences defined by both the "RDATE" and "RRULE".
6566
6567    The recurrence dates, if specified, are used in computing the
6568    recurrence set. The recurrence set is the complete set of recurrence
6569    instances for a calendar component. The recurrence set is generated
6570    by considering the initial "DTSTART" property along with the "RRULE",
6571    "RDATE", "EXDATE" and "EXRULE" properties contained within the
6572    iCalendar object. The "DTSTART" property defines the first instance
6573    in the recurrence set. Multiple instances of the "RRULE" and "EXRULE"
6574    properties can also be specified to define more sophisticated
6575    recurrence sets. The final recurrence set is generated by gathering
6576    all of the start date/times generated by any of the specified "RRULE"
6577    and "RDATE" properties, and excluding any start date/times which fall
6578    within the union of start date/times generated by any specified
6579    "EXRULE" and "EXDATE" properties. This implies that start date/times
6580    within exclusion related properties (i.e., "EXDATE" and "EXRULE")
6581    take precedence over those specified by inclusion properties (i.e.,
6582    "RDATE" and "RRULE"). Where duplicate instances are generated by the
6583    "RRULE" and "RDATE" properties, only one recurrence is considered.
6584    Duplicate instances are ignored.
6585
6586    Format Definition: The property is defined by the following notation:
6587
6588      rdate      = "RDATE" rdtparam ":" rdtval *("," rdtval) CRLF
6589
6590      rdtparam   = *(
6591
6592                 ; the following are optional,
6593                 ; but MUST NOT occur more than once
6594
6595                 (";" "VALUE" "=" ("DATE-TIME" / "DATE" / "PERIOD")) /
6596                 (";" tzidparam) /
6597
6598                 ; the following is optional,
6599                 ; and MAY occur more than once
6600
6601                 (";" xparam)
6602
6603                 )
6604
6605      rdtval     = date-time / date / period
6606      ;Value MUST match value type
6607
6608    Example: The following are examples of this property:
6609
6610
6611
6612
6613 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 116]</span>
6614 </pre><pre class="newpage"><a name="page-117" id="page-117" href="#page-117" class="invisible"> </a>
6615 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6616
6617
6618      RDATE:19970714T123000Z
6619
6620      RDATE;TZID=US-EASTERN:19970714T083000
6621
6622      RDATE;VALUE=PERIOD:19960403T020000Z/19960403T040000Z,
6623       19960404T010000Z/PT3H
6624
6625      RDATE;VALUE=DATE:19970101,19970120,19970217,19970421
6626       19970526,19970704,19970901,19971014,19971128,19971129,19971225
6627
6628 <span class="h5"><h5><a name="section-4.8.5.4">4.8.5.4</a> Recurrence Rule</h5></span>
6629
6630    Property Name: RRULE
6631
6632    Purpose: This property defines a rule or repeating pattern for
6633    recurring events, to-dos, or time zone definitions.
6634
6635    Value Type: RECUR
6636
6637    Property Parameters: Non-standard property parameters can be
6638    specified on this property.
6639
6640    Conformance: This property can be specified one or more times in
6641    recurring "VEVENT", "VTODO" and "VJOURNAL" calendar components. It
6642    can also be specified once in each STANDARD or DAYLIGHT sub-component
6643    of the "VTIMEZONE" calendar component.
6644
6645    Description: The recurrence rule, if specified, is used in computing
6646    the recurrence set. The recurrence set is the complete set of
6647    recurrence instances for a calendar component. The recurrence set is
6648    generated by considering the initial "DTSTART" property along with
6649    the "RRULE", "RDATE", "EXDATE" and "EXRULE" properties contained
6650    within the iCalendar object. The "DTSTART" property defines the first
6651    instance in the recurrence set. Multiple instances of the "RRULE" and
6652    "EXRULE" properties can also be specified to define more
6653    sophisticated recurrence sets. The final recurrence set is generated
6654    by gathering all of the start date/times generated by any of the
6655    specified "RRULE" and "RDATE" properties, and excluding any start
6656    date/times which fall within the union of start date/times generated
6657    by any specified "EXRULE" and "EXDATE" properties. This implies that
6658    start date/times within exclusion related properties (i.e., "EXDATE"
6659    and "EXRULE") take precedence over those specified by inclusion
6660    properties (i.e., "RDATE" and "RRULE"). Where duplicate instances are
6661    generated by the "RRULE" and "RDATE" properties, only one recurrence
6662    is considered. Duplicate instances are ignored.
6663
6664
6665
6666
6667
6668
6669 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 117]</span>
6670 </pre><pre class="newpage"><a name="page-118" id="page-118" href="#page-118" class="invisible"> </a>
6671 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6672
6673
6674    The "DTSTART" and "DTEND" property pair or "DTSTART" and "DURATION"
6675    property pair, specified within the iCalendar object defines the
6676    first instance of the recurrence. When used with a recurrence rule,
6677    the "DTSTART" and "DTEND" properties MUST be specified in local time
6678    and the appropriate set of "VTIMEZONE" calendar components MUST be
6679    included. For detail on the usage of the "VTIMEZONE" calendar
6680    component, see the "VTIMEZONE" calendar component definition.
6681
6682    Any duration associated with the iCalendar object applies to all
6683    members of the generated recurrence set. Any modified duration for
6684    specific recurrences MUST be explicitly specified using the "RDATE"
6685    property.
6686
6687    Format Definition: This property is defined by the following
6688    notation:
6689
6690      rrule      = "RRULE" rrulparam ":" recur CRLF
6691
6692      rrulparam  = *(";" xparam)
6693
6694    Example: All examples assume the Eastern United States time zone.
6695
6696    Daily for 10 occurrences:
6697
6698      DTSTART;TZID=US-Eastern:19970902T090000
6699      RRULE:FREQ=DAILY;COUNT=10
6700
6701      ==&gt; (1997 9:00 AM EDT)September 2-11
6702
6703    Daily until December 24, 1997:
6704
6705      DTSTART;TZID=US-Eastern:19970902T090000
6706      RRULE:FREQ=DAILY;UNTIL=19971224T000000Z
6707
6708      ==&gt; (1997 9:00 AM EDT)September 2-30;October 1-25
6709          (1997 9:00 AM EST)October 26-31;November 1-30;December 1-23
6710
6711    Every other day - forever:
6712
6713      DTSTART;TZID=US-Eastern:19970902T090000
6714      RRULE:FREQ=DAILY;INTERVAL=2
6715      ==&gt; (1997 9:00 AM EDT)September2,4,6,8...24,26,28,30;
6716           October 2,4,6...20,22,24
6717          (1997 9:00 AM EST)October 26,28,30;November 1,3,5,7...25,27,29;
6718           Dec 1,3,...
6719
6720    Every 10 days, 5 occurrences:
6721
6722
6723
6724
6725 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 118]</span>
6726 </pre><pre class="newpage"><a name="page-119" id="page-119" href="#page-119" class="invisible"> </a>
6727 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6728
6729
6730      DTSTART;TZID=US-Eastern:19970902T090000
6731      RRULE:FREQ=DAILY;INTERVAL=10;COUNT=5
6732
6733      ==&gt; (1997 9:00 AM EDT)September 2,12,22;October 2,12
6734
6735    Everyday in January, for 3 years:
6736
6737      DTSTART;TZID=US-Eastern:19980101T090000
6738      RRULE:FREQ=YEARLY;UNTIL=20000131T090000Z;
6739       BYMONTH=1;BYDAY=SU,MO,TU,WE,TH,FR,SA
6740      or
6741      RRULE:FREQ=DAILY;UNTIL=20000131T090000Z;BYMONTH=1
6742
6743      ==&gt; (1998 9:00 AM EDT)January 1-31
6744          (1999 9:00 AM EDT)January 1-31
6745          (2000 9:00 AM EDT)January 1-31
6746
6747    Weekly for 10 occurrences
6748
6749      DTSTART;TZID=US-Eastern:19970902T090000
6750      RRULE:FREQ=WEEKLY;COUNT=10
6751
6752      ==&gt; (1997 9:00 AM EDT)September 2,9,16,23,30;October 7,14,21
6753          (1997 9:00 AM EST)October 28;November 4
6754
6755    Weekly until December 24, 1997
6756
6757      DTSTART;TZID=US-Eastern:19970902T090000
6758      RRULE:FREQ=WEEKLY;UNTIL=19971224T000000Z
6759
6760      ==&gt; (1997 9:00 AM EDT)September 2,9,16,23,30;October 7,14,21
6761          (1997 9:00 AM EST)October 28;November 4,11,18,25;
6762                            December 2,9,16,23
6763    Every other week - forever:
6764
6765      DTSTART;TZID=US-Eastern:19970902T090000
6766      RRULE:FREQ=WEEKLY;INTERVAL=2;WKST=SU
6767
6768      ==&gt; (1997 9:00 AM EDT)September 2,16,30;October 14
6769          (1997 9:00 AM EST)October 28;November 11,25;December 9,23
6770          (1998 9:00 AM EST)January 6,20;February
6771      ...
6772
6773    Weekly on Tuesday and Thursday for 5 weeks:
6774
6775     DTSTART;TZID=US-Eastern:19970902T090000
6776     RRULE:FREQ=WEEKLY;UNTIL=19971007T000000Z;WKST=SU;BYDAY=TU,TH
6777     or
6778
6779
6780
6781 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 119]</span>
6782 </pre><pre class="newpage"><a name="page-120" id="page-120" href="#page-120" class="invisible"> </a>
6783 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6784
6785
6786     RRULE:FREQ=WEEKLY;COUNT=10;WKST=SU;BYDAY=TU,TH
6787
6788     ==&gt; (1997 9:00 AM EDT)September 2,4,9,11,16,18,23,25,30;October 2
6789
6790    Every other week on Monday, Wednesday and Friday until December 24,
6791    1997, but starting on Tuesday, September 2, 1997:
6792
6793      DTSTART;TZID=US-Eastern:19970902T090000
6794      RRULE:FREQ=WEEKLY;INTERVAL=2;UNTIL=19971224T000000Z;WKST=SU;
6795       BYDAY=MO,WE,FR
6796      ==&gt; (1997 9:00 AM EDT)September 2,3,5,15,17,19,29;October
6797      1,3,13,15,17
6798          (1997 9:00 AM EST)October 27,29,31;November 10,12,14,24,26,28;
6799                            December 8,10,12,22
6800
6801    Every other week on Tuesday and Thursday, for 8 occurrences:
6802
6803      DTSTART;TZID=US-Eastern:19970902T090000
6804      RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=8;WKST=SU;BYDAY=TU,TH
6805
6806      ==&gt; (1997 9:00 AM EDT)September 2,4,16,18,30;October 2,14,16
6807
6808    Monthly on the 1st Friday for ten occurrences:
6809
6810      DTSTART;TZID=US-Eastern:19970905T090000
6811      RRULE:FREQ=MONTHLY;COUNT=10;BYDAY=1FR
6812
6813      ==&gt; (1997 9:00 AM EDT)September 5;October 3
6814          (1997 9:00 AM EST)November 7;Dec 5
6815          (1998 9:00 AM EST)January 2;February 6;March 6;April 3
6816          (1998 9:00 AM EDT)May 1;June 5
6817
6818    Monthly on the 1st Friday until December 24, 1997:
6819
6820      DTSTART;TZID=US-Eastern:19970905T090000
6821      RRULE:FREQ=MONTHLY;UNTIL=19971224T000000Z;BYDAY=1FR
6822
6823      ==&gt; (1997 9:00 AM EDT)September 5;October 3
6824          (1997 9:00 AM EST)November 7;December 5
6825
6826    Every other month on the 1st and last Sunday of the month for 10
6827    occurrences:
6828
6829      DTSTART;TZID=US-Eastern:19970907T090000
6830      RRULE:FREQ=MONTHLY;INTERVAL=2;COUNT=10;BYDAY=1SU,-1SU
6831
6832      ==&gt; (1997 9:00 AM EDT)September 7,28
6833          (1997 9:00 AM EST)November 2,30
6834
6835
6836
6837 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 120]</span>
6838 </pre><pre class="newpage"><a name="page-121" id="page-121" href="#page-121" class="invisible"> </a>
6839 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6840
6841
6842          (1998 9:00 AM EST)January 4,25;March 1,29
6843          (1998 9:00 AM EDT)May 3,31
6844
6845    Monthly on the second to last Monday of the month for 6 months:
6846
6847      DTSTART;TZID=US-Eastern:19970922T090000
6848      RRULE:FREQ=MONTHLY;COUNT=6;BYDAY=-2MO
6849
6850      ==&gt; (1997 9:00 AM EDT)September 22;October 20
6851          (1997 9:00 AM EST)November 17;December 22
6852          (1998 9:00 AM EST)January 19;February 16
6853
6854    Monthly on the third to the last day of the month, forever:
6855
6856      DTSTART;TZID=US-Eastern:19970928T090000
6857      RRULE:FREQ=MONTHLY;BYMONTHDAY=-3
6858
6859      ==&gt; (1997 9:00 AM EDT)September 28
6860          (1997 9:00 AM EST)October 29;November 28;December 29
6861          (1998 9:00 AM EST)January 29;February 26
6862      ...
6863
6864    Monthly on the 2nd and 15th of the month for 10 occurrences:
6865
6866      DTSTART;TZID=US-Eastern:19970902T090000
6867      RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=2,15
6868
6869      ==&gt; (1997 9:00 AM EDT)September 2,15;October 2,15
6870          (1997 9:00 AM EST)November 2,15;December 2,15
6871          (1998 9:00 AM EST)January 2,15
6872
6873    Monthly on the first and last day of the month for 10 occurrences:
6874
6875      DTSTART;TZID=US-Eastern:19970930T090000
6876      RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=1,-1
6877
6878      ==&gt; (1997 9:00 AM EDT)September 30;October 1
6879          (1997 9:00 AM EST)October 31;November 1,30;December 1,31
6880          (1998 9:00 AM EST)January 1,31;February 1
6881
6882    Every 18 months on the 10th thru 15th of the month for 10
6883    occurrences:
6884
6885      DTSTART;TZID=US-Eastern:19970910T090000
6886      RRULE:FREQ=MONTHLY;INTERVAL=18;COUNT=10;BYMONTHDAY=10,11,12,13,14,
6887       15
6888
6889      ==&gt; (1997 9:00 AM EDT)September 10,11,12,13,14,15
6890
6891
6892
6893 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 121]</span>
6894 </pre><pre class="newpage"><a name="page-122" id="page-122" href="#page-122" class="invisible"> </a>
6895 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6896
6897
6898          (1999 9:00 AM EST)March 10,11,12,13
6899
6900    Every Tuesday, every other month:
6901
6902      DTSTART;TZID=US-Eastern:19970902T090000
6903      RRULE:FREQ=MONTHLY;INTERVAL=2;BYDAY=TU
6904
6905      ==&gt; (1997 9:00 AM EDT)September 2,9,16,23,30
6906          (1997 9:00 AM EST)November 4,11,18,25
6907          (1998 9:00 AM EST)January 6,13,20,27;March 3,10,17,24,31
6908      ...
6909
6910    Yearly in June and July for 10 occurrences:
6911
6912      DTSTART;TZID=US-Eastern:19970610T090000
6913      RRULE:FREQ=YEARLY;COUNT=10;BYMONTH=6,7
6914      ==&gt; (1997 9:00 AM EDT)June 10;July 10
6915          (1998 9:00 AM EDT)June 10;July 10
6916          (1999 9:00 AM EDT)June 10;July 10
6917          (2000 9:00 AM EDT)June 10;July 10
6918          (2001 9:00 AM EDT)June 10;July 10
6919      Note: Since none of the BYDAY, BYMONTHDAY or BYYEARDAY components
6920      are specified, the day is gotten from DTSTART
6921
6922    Every other year on January, February, and March for 10 occurrences:
6923
6924      DTSTART;TZID=US-Eastern:19970310T090000
6925      RRULE:FREQ=YEARLY;INTERVAL=2;COUNT=10;BYMONTH=1,2,3
6926
6927      ==&gt; (1997 9:00 AM EST)March 10
6928          (1999 9:00 AM EST)January 10;February 10;March 10
6929          (2001 9:00 AM EST)January 10;February 10;March 10
6930          (2003 9:00 AM EST)January 10;February 10;March 10
6931
6932    Every 3rd year on the 1st, 100th and 200th day for 10 occurrences:
6933
6934      DTSTART;TZID=US-Eastern:19970101T090000
6935      RRULE:FREQ=YEARLY;INTERVAL=3;COUNT=10;BYYEARDAY=1,100,200
6936
6937      ==&gt; (1997 9:00 AM EST)January 1
6938          (1997 9:00 AM EDT)April 10;July 19
6939          (2000 9:00 AM EST)January 1
6940          (2000 9:00 AM EDT)April 9;July 18
6941          (2003 9:00 AM EST)January 1
6942          (2003 9:00 AM EDT)April 10;July 19
6943          (2006 9:00 AM EST)January 1
6944
6945    Every 20th Monday of the year, forever:
6946
6947
6948
6949 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 122]</span>
6950 </pre><pre class="newpage"><a name="page-123" id="page-123" href="#page-123" class="invisible"> </a>
6951 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
6952
6953
6954      DTSTART;TZID=US-Eastern:19970519T090000
6955      RRULE:FREQ=YEARLY;BYDAY=20MO
6956
6957      ==&gt; (1997 9:00 AM EDT)May 19
6958          (1998 9:00 AM EDT)May 18
6959          (1999 9:00 AM EDT)May 17
6960      ...
6961
6962    Monday of week number 20 (where the default start of the week is
6963    Monday), forever:
6964
6965      DTSTART;TZID=US-Eastern:19970512T090000
6966      RRULE:FREQ=YEARLY;BYWEEKNO=20;BYDAY=MO
6967
6968      ==&gt; (1997 9:00 AM EDT)May 12
6969          (1998 9:00 AM EDT)May 11
6970          (1999 9:00 AM EDT)May 17
6971      ...
6972
6973    Every Thursday in March, forever:
6974
6975      DTSTART;TZID=US-Eastern:19970313T090000
6976      RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=TH
6977
6978      ==&gt; (1997 9:00 AM EST)March 13,20,27
6979          (1998 9:00 AM EST)March 5,12,19,26
6980          (1999 9:00 AM EST)March 4,11,18,25
6981      ...
6982
6983    Every Thursday, but only during June, July, and August, forever:
6984
6985      DTSTART;TZID=US-Eastern:19970605T090000
6986      RRULE:FREQ=YEARLY;BYDAY=TH;BYMONTH=6,7,8
6987
6988      ==&gt; (1997 9:00 AM EDT)June 5,12,19,26;July 3,10,17,24,31;
6989                        August 7,14,21,28
6990          (1998 9:00 AM EDT)June 4,11,18,25;July 2,9,16,23,30;
6991                        August 6,13,20,27
6992          (1999 9:00 AM EDT)June 3,10,17,24;July 1,8,15,22,29;
6993                        August 5,12,19,26
6994      ...
6995
6996    Every Friday the 13th, forever:
6997
6998      DTSTART;TZID=US-Eastern:19970902T090000
6999      EXDATE;TZID=US-Eastern:19970902T090000
7000      RRULE:FREQ=MONTHLY;BYDAY=FR;BYMONTHDAY=13
7001
7002
7003
7004
7005 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 123]</span>
7006 </pre><pre class="newpage"><a name="page-124" id="page-124" href="#page-124" class="invisible"> </a>
7007 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7008
7009
7010      ==&gt; (1998 9:00 AM EST)February 13;March 13;November 13
7011          (1999 9:00 AM EDT)August 13
7012          (2000 9:00 AM EDT)October 13
7013      ...
7014
7015    The first Saturday that follows the first Sunday of the month,
7016     forever:
7017
7018      DTSTART;TZID=US-Eastern:19970913T090000
7019      RRULE:FREQ=MONTHLY;BYDAY=SA;BYMONTHDAY=7,8,9,10,11,12,13
7020
7021      ==&gt; (1997 9:00 AM EDT)September 13;October 11
7022          (1997 9:00 AM EST)November 8;December 13
7023          (1998 9:00 AM EST)January 10;February 7;March 7
7024          (1998 9:00 AM EDT)April 11;May 9;June 13...
7025      ...
7026
7027    Every four years, the first Tuesday after a Monday in November,
7028    forever (U.S. Presidential Election day):
7029
7030      DTSTART;TZID=US-Eastern:19961105T090000
7031      RRULE:FREQ=YEARLY;INTERVAL=4;BYMONTH=11;BYDAY=TU;BYMONTHDAY=2,3,4,
7032       5,6,7,8
7033
7034      ==&gt; (1996 9:00 AM EST)November 5
7035          (2000 9:00 AM EST)November 7
7036          (2004 9:00 AM EST)November 2
7037      ...
7038
7039    The 3rd instance into the month of one of Tuesday, Wednesday or
7040    Thursday, for the next 3 months:
7041
7042      DTSTART;TZID=US-Eastern:19970904T090000
7043      RRULE:FREQ=MONTHLY;COUNT=3;BYDAY=TU,WE,TH;BYSETPOS=3
7044
7045      ==&gt; (1997 9:00 AM EDT)September 4;October 7
7046          (1997 9:00 AM EST)November 6
7047
7048    The 2nd to last weekday of the month:
7049
7050      DTSTART;TZID=US-Eastern:19970929T090000
7051      RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-2
7052
7053      ==&gt; (1997 9:00 AM EDT)September 29
7054          (1997 9:00 AM EST)October 30;November 27;December 30
7055          (1998 9:00 AM EST)January 29;February 26;March 30
7056      ...
7057
7058
7059
7060
7061 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 124]</span>
7062 </pre><pre class="newpage"><a name="page-125" id="page-125" href="#page-125" class="invisible"> </a>
7063 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7064
7065
7066    Every 3 hours from 9:00 AM to 5:00 PM on a specific day:
7067
7068      DTSTART;TZID=US-Eastern:19970902T090000
7069      RRULE:FREQ=HOURLY;INTERVAL=3;UNTIL=19970902T170000Z
7070
7071      ==&gt; (September 2, 1997 EDT)09:00,12:00,15:00
7072
7073    Every 15 minutes for 6 occurrences:
7074
7075      DTSTART;TZID=US-Eastern:19970902T090000
7076      RRULE:FREQ=MINUTELY;INTERVAL=15;COUNT=6
7077
7078      ==&gt; (September 2, 1997 EDT)09:00,09:15,09:30,09:45,10:00,10:15
7079
7080    Every hour and a half for 4 occurrences:
7081
7082      DTSTART;TZID=US-Eastern:19970902T090000
7083      RRULE:FREQ=MINUTELY;INTERVAL=90;COUNT=4
7084
7085      ==&gt; (September 2, 1997 EDT)09:00,10:30;12:00;13:30
7086
7087    Every 20 minutes from 9:00 AM to 4:40 PM every day:
7088
7089      DTSTART;TZID=US-Eastern:19970902T090000
7090      RRULE:FREQ=DAILY;BYHOUR=9,10,11,12,13,14,15,16;BYMINUTE=0,20,40
7091      or
7092      RRULE:FREQ=MINUTELY;INTERVAL=20;BYHOUR=9,10,11,12,13,14,15,16
7093
7094      ==&gt; (September 2, 1997 EDT)9:00,9:20,9:40,10:00,10:20,
7095                                 ... 16:00,16:20,16:40
7096          (September 3, 1997 EDT)9:00,9:20,9:40,10:00,10:20,
7097                                ...16:00,16:20,16:40
7098      ...
7099
7100    An example where the days generated makes a difference because of
7101    WKST:
7102
7103      DTSTART;TZID=US-Eastern:19970805T090000
7104      RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=MO
7105
7106      ==&gt; (1997 EDT)Aug 5,10,19,24
7107
7108      changing only WKST from MO to SU, yields different results...
7109
7110      DTSTART;TZID=US-Eastern:19970805T090000
7111      RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=SU
7112      ==&gt; (1997 EDT)August 5,17,19,31
7113
7114
7115
7116
7117 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 125]</span>
7118 </pre><pre class="newpage"><a name="page-126" id="page-126" href="#page-126" class="invisible"> </a>
7119 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7120
7121
7122 <span class="h4"><h4><a name="section-4.8.6">4.8.6</a> Alarm Component Properties</h4></span>
7123
7124    The following properties specify alarm information in calendar
7125    components.
7126
7127 <span class="h5"><h5><a name="section-4.8.6.1">4.8.6.1</a> Action</h5></span>
7128
7129    Property Name: ACTION
7130
7131    Purpose: This property defines the action to be invoked when an alarm
7132    is triggered.
7133
7134    Value Type: TEXT
7135
7136    Property Parameters: Non-standard property parameters can be
7137    specified on this property.
7138
7139    Conformance: This property MUST be specified once in a "VALARM"
7140    calendar component.
7141
7142    Description: Each "VALARM" calendar component has a particular type
7143    of action associated with it. This property specifies the type of
7144    action
7145
7146    Format Definition: The property is defined by the following notation:
7147
7148      action     = "ACTION" actionparam ":" actionvalue CRLF
7149
7150      actionparam        = *(";" xparam)
7151
7152      actionvalue        = "AUDIO" / "DISPLAY" / "EMAIL" / "PROCEDURE"
7153                         / iana-token / x-name
7154
7155    Example: The following are examples of this property in a "VALARM"
7156    calendar component:
7157
7158      ACTION:AUDIO
7159
7160      ACTION:DISPLAY
7161
7162      ACTION:PROCEDURE
7163
7164 <span class="h5"><h5><a name="section-4.8.6.2">4.8.6.2</a> Repeat Count</h5></span>
7165
7166    Property Name: REPEAT
7167
7168    Purpose: This property defines the number of time the alarm should be
7169    repeated, after the initial trigger.
7170
7171
7172
7173 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 126]</span>
7174 </pre><pre class="newpage"><a name="page-127" id="page-127" href="#page-127" class="invisible"> </a>
7175 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7176
7177
7178    Value Type: INTEGER
7179
7180    Property Parameters: Non-standard property parameters can be
7181    specified on this property.
7182
7183    Conformance: This property can be specified in a "VALARM" calendar
7184    component.
7185
7186    Description: If the alarm triggers more than once, then this property
7187    MUST be specified along with the "DURATION" property.
7188
7189    Format Definition: The property is defined by the following notation:
7190
7191      repeatcnt  = "REPEAT" repparam ":" integer CRLF
7192      ;Default is "0", zero.
7193
7194      repparam   = *(";" xparam)
7195
7196    Example: The following is an example of this property for an alarm
7197    that repeats 4 additional times with a 5 minute delay after the
7198    initial triggering of the alarm:
7199
7200      REPEAT:4
7201      DURATION:PT5M
7202
7203 <span class="h5"><h5><a name="section-4.8.6.3">4.8.6.3</a> Trigger</h5></span>
7204
7205    Property Name: TRIGGER
7206
7207    Purpose: This property specifies when an alarm will trigger.
7208
7209    Value Type: The default value type is DURATION. The value type can be
7210    set to a DATE-TIME value type, in which case the value MUST specify a
7211    UTC formatted DATE-TIME value.
7212
7213    Property Parameters: Non-standard, value data type, time zone
7214    identifier or trigger relationship property parameters can be
7215    specified on this property. The trigger relationship property
7216    parameter MUST only be specified when the value type is DURATION.
7217
7218    Conformance: This property MUST be specified in the "VALARM" calendar
7219    component.
7220
7221    Description: Within the "VALARM" calendar component, this property
7222    defines when the alarm will trigger. The default value type is
7223    DURATION, specifying a relative time for the trigger of the alarm.
7224    The default duration is relative to the start of an event or to-do
7225    that the alarm is associated with. The duration can be explicitly set
7226
7227
7228
7229 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 127]</span>
7230 </pre><pre class="newpage"><a name="page-128" id="page-128" href="#page-128" class="invisible"> </a>
7231 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7232
7233
7234    to trigger from either the end or the start of the associated event
7235    or to-do with the "RELATED" parameter. A value of START will set the
7236    alarm to trigger off the start of the associated event or to-do. A
7237    value of END will set the alarm to trigger off the end of the
7238    associated event or to-do.
7239
7240    Either a positive or negative duration may be specified for the
7241    "TRIGGER" property. An alarm with a positive duration is triggered
7242    after the associated start or end of the event or to-do. An alarm
7243    with a negative duration is triggered before the associated start or
7244    end of the event or to-do.
7245
7246    The "RELATED" property parameter is not valid if the value type of
7247    the property is set to DATE-TIME (i.e., for an absolute date and time
7248    alarm trigger). If a value type of DATE-TIME is specified, then the
7249    property value MUST be specified in the UTC time format. If an
7250    absolute trigger is specified on an alarm for a recurring event or
7251    to-do, then the alarm will only trigger for the specified absolute
7252    date/time, along with any specified repeating instances.
7253
7254    If the trigger is set relative to START, then the "DTSTART" property
7255    MUST be present in the associated "VEVENT" or "VTODO" calendar
7256    component. If an alarm is specified for an event with the trigger set
7257    relative to the END, then the "DTEND" property or the "DSTART" and
7258    "DURATION' properties MUST be present in the associated "VEVENT"
7259    calendar component. If the alarm is specified for a to-do with a
7260    trigger set relative to the END, then either the "DUE" property or
7261    the "DSTART" and "DURATION' properties MUST be present in the
7262    associated "VTODO" calendar component.
7263
7264    Alarms specified in an event or to-do which is defined in terms of a
7265    DATE value type will be triggered relative to 00:00:00 UTC on the
7266    specified date. For example, if "DTSTART:19980205, then the duration
7267    trigger will be relative to19980205T000000Z.
7268
7269    Format Definition: The property is defined by the following notation:
7270
7271      trigger    = "TRIGGER" (trigrel / trigabs)
7272
7273      trigrel    = *(
7274
7275                 ; the following are optional,
7276                 ; but MUST NOT occur more than once
7277
7278                   (";" "VALUE" "=" "DURATION") /
7279                   (";" trigrelparam) /
7280
7281                 ; the following is optional,
7282
7283
7284
7285 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 128]</span>
7286 </pre><pre class="newpage"><a name="page-129" id="page-129" href="#page-129" class="invisible"> </a>
7287 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7288
7289
7290                 ; and MAY occur more than once
7291
7292                   (";" xparam)
7293                   ) ":"  dur-value
7294
7295      trigabs    = 1*(
7296
7297                 ; the following is REQUIRED,
7298                 ; but MUST NOT occur more than once
7299
7300                   (";" "VALUE" "=" "DATE-TIME") /
7301
7302                 ; the following is optional,
7303                 ; and MAY occur more than once
7304
7305                   (";" xparam)
7306
7307                   ) ":" date-time
7308
7309    Example: A trigger set 15 minutes prior to the start of the event or
7310    to-do.
7311
7312      TRIGGER:-P15M
7313
7314    A trigger set 5 minutes after the end of the event or to-do.
7315
7316      TRIGGER;RELATED=END:P5M
7317
7318    A trigger set to an absolute date/time.
7319
7320      TRIGGER;VALUE=DATE-TIME:19980101T050000Z
7321
7322 <span class="h4"><h4><a name="section-4.8.7">4.8.7</a> Change Management Component Properties</h4></span>
7323
7324    The following properties specify change management information in
7325    calendar components.
7326
7327 <span class="h5"><h5><a name="section-4.8.7.1">4.8.7.1</a> Date/Time Created</h5></span>
7328
7329    Property Name: CREATED
7330
7331    Purpose: This property specifies the date and time that the calendar
7332    information was created by the calendar user agent in the calendar
7333    store.
7334
7335         Note: This is analogous to the creation date and time for a file
7336         in the file system.
7337
7338
7339
7340
7341 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 129]</span>
7342 </pre><pre class="newpage"><a name="page-130" id="page-130" href="#page-130" class="invisible"> </a>
7343 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7344
7345
7346    Value Type: DATE-TIME
7347
7348    Property Parameters: Non-standard property parameters can be
7349    specified on this property.
7350
7351    Conformance: The property can be specified once in "VEVENT", "VTODO"
7352    or "VJOURNAL" calendar components.
7353
7354    Description: The date and time is a UTC value.
7355
7356    Format Definition: The property is defined by the following notation:
7357
7358      created    = "CREATED" creaparam ":" date-time CRLF
7359
7360      creaparam  = *(";" xparam)
7361
7362    Example: The following is an example of this property:
7363
7364      CREATED:19960329T133000Z
7365
7366 <span class="h5"><h5><a name="section-4.8.7.2">4.8.7.2</a> Date/Time Stamp</h5></span>
7367
7368    Property Name: DTSTAMP
7369
7370    Purpose: The property indicates the date/time that the instance of
7371    the iCalendar object was created.
7372
7373    Value Type: DATE-TIME
7374
7375    Property Parameters: Non-standard property parameters can be
7376    specified on this property.
7377
7378    Conformance: This property MUST be included in the "VEVENT", "VTODO",
7379    "VJOURNAL" or "VFREEBUSY" calendar components.
7380
7381    Description: The value MUST be specified in the UTC time format.
7382
7383    This property is also useful to protocols such as [<a href="#ref-IMIP" title="&quot;iCalendar Message-based Interoperability Protocol (IMIP)&quot;">IMIP</a>] that have
7384    inherent latency issues with the delivery of content. This property
7385    will assist in the proper sequencing of messages containing iCalendar
7386    objects.
7387
7388    This property is different than the "CREATED" and "LAST-MODIFIED"
7389    properties. These two properties are used to specify when the
7390    particular calendar data in the calendar store was created and last
7391    modified. This is different than when the iCalendar object
7392    representation of the calendar service information was created or
7393    last modified.
7394
7395
7396
7397 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 130]</span>
7398 </pre><pre class="newpage"><a name="page-131" id="page-131" href="#page-131" class="invisible"> </a>
7399 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7400
7401
7402    Format Definition: The property is defined by the following notation:
7403
7404      dtstamp    = "DTSTAMP" stmparam ":" date-time CRLF
7405
7406      stmparam   = *(";" xparam)
7407
7408    Example:
7409
7410      DTSTAMP:19971210T080000Z
7411
7412 <span class="h5"><h5><a name="section-4.8.7.3">4.8.7.3</a> Last Modified</h5></span>
7413
7414    Property Name: LAST-MODIFIED
7415
7416    Purpose: The property specifies the date and time that the
7417    information associated with the calendar component was last revised
7418    in the calendar store.
7419
7420         Note: This is analogous to the modification date and time for a
7421         file in the file system.
7422
7423    Value Type: DATE-TIME
7424
7425    Property Parameters: Non-standard property parameters can be
7426    specified on this property.
7427
7428    Conformance: This property can be specified in the "EVENT", "VTODO",
7429    "VJOURNAL" or "VTIMEZONE" calendar components.
7430
7431    Description: The property value MUST be specified in the UTC time
7432    format.
7433
7434    Format Definition: The property is defined by the following notation:
7435
7436      last-mod   = "LAST-MODIFIED" lstparam ":" date-time CRLF
7437
7438      lstparam   = *(";" xparam)
7439
7440    Example: The following is are examples of this property:
7441
7442      LAST-MODIFIED:19960817T133000Z
7443
7444 <span class="h5"><h5><a name="section-4.8.7.4">4.8.7.4</a> Sequence Number</h5></span>
7445
7446    Property Name: SEQUENCE
7447
7448    Purpose: This property defines the revision sequence number of the
7449    calendar component within a sequence of revisions.
7450
7451
7452
7453 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 131]</span>
7454 </pre><pre class="newpage"><a name="page-132" id="page-132" href="#page-132" class="invisible"> </a>
7455 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7456
7457
7458    Value Type: integer
7459
7460    Property Parameters: Non-standard property parameters can be
7461    specified on this property.
7462
7463    Conformance: The property can be specified in "VEVENT", "VTODO" or
7464    "VJOURNAL" calendar component.
7465
7466    Description: When a calendar component is created, its sequence
7467    number is zero (US-ASCII decimal 48). It is monotonically incremented
7468    by the "Organizer's" CUA each time the "Organizer" makes a
7469    significant revision to the calendar component. When the "Organizer"
7470    makes changes to one of the following properties, the sequence number
7471    MUST be incremented:
7472
7473      .  "DTSTART"
7474
7475      .  "DTEND"
7476
7477      .  "DUE"
7478
7479      .  "RDATE"
7480
7481      .  "RRULE"
7482
7483      .  "EXDATE"
7484
7485      .  "EXRULE"
7486
7487      .  "STATUS"
7488
7489    In addition, changes made by the "Organizer" to other properties can
7490    also force the sequence number to be incremented. The "Organizer" CUA
7491    MUST increment the sequence number when ever it makes changes to
7492    properties in the calendar component that the "Organizer" deems will
7493    jeopardize the validity of the participation status of the
7494    "Attendees". For example, changing the location of a meeting from one
7495    locale to another distant locale could effectively impact the
7496    participation status of the "Attendees".
7497
7498    The "Organizer" includes this property in an iCalendar object that it
7499    sends to an "Attendee" to specify the current version of the calendar
7500    component.
7501
7502    The "Attendee" includes this property in an iCalendar object that it
7503    sends to the "Organizer" to specify the version of the calendar
7504    component that the "Attendee" is referring to.
7505
7506
7507
7508
7509 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 132]</span>
7510 </pre><pre class="newpage"><a name="page-133" id="page-133" href="#page-133" class="invisible"> </a>
7511 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7512
7513
7514    A change to the sequence number is not the mechanism that an
7515    "Organizer" uses to request a response from the "Attendees". The
7516    "RSVP" parameter on the "ATTENDEE" property is used by the
7517    "Organizer" to indicate that a response from the "Attendees" is
7518    requested.
7519
7520    Format Definition: This property is defined by the following
7521    notation:
7522
7523      seq = "SEQUENCE" seqparam ":" integer CRLF
7524      ; Default is "0"
7525
7526      seqparam   = *(";" xparam)
7527
7528    Example: The following is an example of this property for a calendar
7529    component that was just created by the "Organizer".
7530
7531      SEQUENCE:0
7532
7533    The following is an example of this property for a calendar component
7534    that has been revised two different times by the "Organizer".
7535
7536      SEQUENCE:2
7537
7538 <span class="h4"><h4><a name="section-4.8.8">4.8.8</a> Miscellaneous Component Properties</h4></span>
7539
7540    The following properties specify information about a number of
7541    miscellaneous features of calendar components.
7542
7543 <span class="h5"><h5><a name="section-4.8.8.1">4.8.8.1</a> Non-standard Properties</h5></span>
7544
7545    Property Name: Any property name with a "X-" prefix
7546
7547    Purpose: This class of property provides a framework for defining
7548    non-standard properties.
7549
7550    Value Type: TEXT
7551
7552    Property Parameters: Non-standard and language property parameters
7553    can be specified on this property.
7554
7555    Conformance: This property can be specified in any calendar
7556    component.
7557
7558    Description: The MIME Calendaring and Scheduling Content Type
7559    provides a "standard mechanism for doing non-standard things". This
7560    extension support is provided for implementers to "push the envelope"
7561    on the existing version of the memo. Extension properties are
7562
7563
7564
7565 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 133]</span>
7566 </pre><pre class="newpage"><a name="page-134" id="page-134" href="#page-134" class="invisible"> </a>
7567 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7568
7569
7570    specified by property and/or property parameter names that have the
7571    prefix text of "X-" (the two character sequence: LATIN CAPITAL LETTER
7572    X character followed by the HYPEN-MINUS character). It is recommended
7573    that vendors concatenate onto this sentinel another short prefix text
7574    to identify the vendor. This will facilitate readability of the
7575    extensions and minimize possible collision of names between different
7576    vendors. User agents that support this content type are expected to
7577    be able to parse the extension properties and property parameters but
7578    can ignore them.
7579
7580    At present, there is no registration authority for names of extension
7581    properties and property parameters. The data type for this property
7582    is TEXT. Optionally, the data type can be any of the other valid data
7583    types.
7584
7585    Format Definition: The property is defined by the following notation:
7586
7587      x-prop     = x-name *(";" xparam) [";" languageparam] ":" text CRLF
7588         ; Lines longer than 75 octets should be folded
7589
7590    Example: The following might be the ABC vendor's extension for an
7591    audio-clip form of subject property:
7592
7593      X-ABC-MMSUBJ;X-ABC-MMSUBJTYPE=wave:http://load.noise.org/mysubj.wav
7594
7595 <span class="h5"><h5><a name="section-4.8.8.2">4.8.8.2</a> Request Status</h5></span>
7596
7597    Property Name: REQUEST-STATUS
7598
7599    Purpose: This property defines the status code returned for a
7600    scheduling request.
7601
7602    Value Type: TEXT
7603
7604    Property Parameters: Non-standard and language property parameters
7605    can be specified on this property.
7606
7607    Conformance: The property can be specified in "VEVENT", "VTODO",
7608    "VJOURNAL" or "VFREEBUSY" calendar component.
7609
7610    Description: This property is used to return status code information
7611    related to the processing of an associated iCalendar object. The data
7612    type for this property is TEXT.
7613
7614    The value consists of a short return status component, a longer
7615    return status description component, and optionally a status-specific
7616    data component. The components of the value are separated by the
7617    SEMICOLON character (US-ASCII decimal 59).
7618
7619
7620
7621 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 134]</span>
7622 </pre><pre class="newpage"><a name="page-135" id="page-135" href="#page-135" class="invisible"> </a>
7623 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7624
7625
7626    The short return status is a PERIOD character (US-ASCII decimal 46)
7627    separated 3-tuple of integers. For example, "3.1.1". The successive
7628    levels of integers provide for a successive level of status code
7629    granularity.
7630
7631    The following are initial classes for the return status code.
7632    Individual iCalendar object methods will define specific return
7633    status codes for these classes. In addition, other classes for the
7634    return status code may be defined using the registration process
7635    defined later in this memo.
7636
7637      |==============+===============================================|
7638      | Short Return | Longer Return Status Description              |
7639      | Status Code  |                                               |
7640      |==============+===============================================|
7641      |    1.xx      | Preliminary success. This class of status     |
7642      |              | of status code indicates that the request has |
7643      |              | request has been initially processed but that |
7644      |              | completion is pending.                        |
7645      |==============+===============================================|
7646      |    2.xx      | Successful. This class of status code         |
7647      |              | indicates that the request was completed      |
7648      |              | successfuly. However, the exact status code   |
7649      |              | can indicate that a fallback has been taken.  |
7650      |==============+===============================================|
7651      |    3.xx      | Client Error. This class of status code       |
7652      |              | indicates that the request was not successful.|
7653      |              | The error is the result of either a syntax or |
7654      |              | a semantic error in the client formatted      |
7655      |              | request. Request should not be retried until  |
7656      |              | the condition in the request is corrected.    |
7657      |==============+===============================================|
7658      |    4.xx      | Scheduling Error. This class of status code   |
7659      |              | indicates that the request was not successful.|
7660      |              | Some sort of error occurred within the        |
7661      |              | calendaring and scheduling service, not       |
7662      |              | directly related to the request itself.       |
7663      |==============+===============================================|
7664
7665    Format Definition: The property is defined by the following notation:
7666
7667      rstatus    = "REQUEST-STATUS" rstatparam ":"
7668                   statcode ";" statdesc [";" extdata]
7669
7670      rstatparam = *(
7671
7672                 ; the following is optional,
7673                 ; but MUST NOT occur more than once
7674
7675
7676
7677 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 135]</span>
7678 </pre><pre class="newpage"><a name="page-136" id="page-136" href="#page-136" class="invisible"> </a>
7679 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7680
7681
7682                 (";" languageparm) /
7683
7684                 ; the following is optional,
7685                 ; and MAY occur more than once
7686
7687                 (";" xparam)
7688
7689                 )
7690
7691      statcode   = 1*DIGIT *("." 1*DIGIT)
7692      ;Hierarchical, numeric return status code
7693
7694      statdesc   = text
7695      ;Textual status description
7696
7697      extdata    = text
7698      ;Textual exception data. For example, the offending property
7699      ;name and value or complete property line.
7700
7701    Example: The following are some possible examples of this property.
7702    The COMMA and SEMICOLON separator characters in the property value
7703    are BACKSLASH character escaped because they appear in a  text value.
7704
7705      REQUEST-STATUS:2.0;Success
7706
7707      REQUEST-STATUS:3.1;Invalid property value;DTSTART:96-Apr-01
7708
7709      REQUEST-STATUS:2.8; Success\, repeating event ignored. Scheduled
7710       as a single event.;RRULE:FREQ=WEEKLY\;INTERVAL=2
7711
7712      REQUEST-STATUS:4.1;Event conflict. Date/time is busy.
7713
7714      REQUEST-STATUS:3.7;Invalid calendar user;ATTENDEE:
7715       MAILTO:jsmith@host.com
7716
7717 <span class="h2"><h2><a name="section-5">5</a> iCalendar Object Examples</h2></span>
7718
7719    The following examples are provided as an informational source of
7720    illustrative iCalendar objects consistent with this content type.
7721
7722    The following example specifies a three-day conference that begins at
7723    8:00 AM EDT, September 18, 1996 and end at 6:00 PM EDT, September 20,
7724    1996.
7725
7726      BEGIN:VCALENDAR PRODID:-//xyz Corp//NONSGML PDA Calendar Verson
7727      1.0//EN VERSION:2.0 BEGIN:VEVENT DTSTAMP:19960704T120000Z
7728      UID:uid1@host.com ORGANIZER:MAILTO:jsmith@host.com
7729      DTSTART:19960918T143000Z DTEND:19960920T220000Z STATUS:CONFIRMED
7730
7731
7732
7733 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 136]</span>
7734 </pre><pre class="newpage"><a name="page-137" id="page-137" href="#page-137" class="invisible"> </a>
7735 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7736
7737
7738      CATEGORIES:CONFERENCE SUMMARY:Networld+Interop Conference
7739      DESCRIPTION:Networld+Interop Conference
7740        and Exhibit\nAtlanta World Congress Center\n
7741       Atlanta, Georgia END:VEVENT END:VCALENDAR
7742
7743    The following example specifies a group scheduled meeting that begin
7744    at 8:30 AM EST on March 12, 1998 and end at 9:30 AM EST on March 12,
7745    1998. The "Organizer" has scheduled the meeting with one or more
7746    calendar users in a group. A time zone specification for Eastern
7747    United States has been specified.
7748
7749      BEGIN:VCALENDAR
7750      PRODID:-//RDU Software//NONSGML HandCal//EN
7751      VERSION:2.0
7752      BEGIN:VTIMEZONE
7753      TZID:US-Eastern
7754      BEGIN:STANDARD
7755      DTSTART:19981025T020000
7756      RDATE:19981025T020000
7757      TZOFFSETFROM:-0400
7758      TZOFFSETTO:-0500
7759      TZNAME:EST
7760      END:STANDARD
7761      BEGIN:DAYLIGHT
7762      DTSTART:19990404T020000
7763      RDATE:19990404T020000
7764      TZOFFSETFROM:-0500
7765      TZOFFSETTO:-0400
7766      TZNAME:EDT
7767      END:DAYLIGHT
7768      END:VTIMEZONE
7769      BEGIN:VEVENT
7770      DTSTAMP:19980309T231000Z
7771      UID:guid-1.host1.com
7772      ORGANIZER;ROLE=CHAIR:MAILTO:mrbig@host.com
7773      ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT;CUTYPE=GROUP:
7774       MAILTO:employee-A@host.com
7775      DESCRIPTION:Project XYZ Review Meeting
7776      CATEGORIES:MEETING
7777      CLASS:PUBLIC
7778      CREATED:19980309T130000Z
7779      SUMMARY:XYZ Project Review
7780      DTSTART;TZID=US-Eastern:19980312T083000
7781      DTEND;TZID=US-Eastern:19980312T093000
7782      LOCATION:1CP Conference Room 4350
7783      END:VEVENT
7784      END:VCALENDAR
7785
7786
7787
7788
7789 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 137]</span>
7790 </pre><pre class="newpage"><a name="page-138" id="page-138" href="#page-138" class="invisible"> </a>
7791 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7792
7793
7794    The following is an example of an iCalendar object passed in a MIME
7795    message with a single body part consisting of a "text/calendar"
7796    Content Type.
7797
7798      TO:jsmith@host1.com
7799      FROM:jdoe@host1.com
7800      MIME-VERSION:1.0
7801      MESSAGE-ID:&lt;id3@host1.com&gt;
7802      CONTENT-TYPE:text/calendar
7803
7804      BEGIN:VCALENDAR
7805      METHOD:xyz
7806      VERSION:2.0
7807      PRODID:-//ABC Corporation//NONSGML My Product//EN
7808      BEGIN:VEVENT
7809      DTSTAMP:19970324T1200Z
7810      SEQUENCE:0
7811      UID:uid3@host1.com
7812      ORGANIZER:MAILTO:jdoe@host1.com
7813      ATTENDEE;RSVP=TRUE:MAILTO:jsmith@host1.com
7814      DTSTART:19970324T123000Z
7815      DTEND:19970324T210000Z
7816      CATEGORIES:MEETING,PROJECT
7817      CLASS:PUBLIC
7818      SUMMARY:Calendaring Interoperability Planning Meeting
7819      DESCRIPTION:Discuss how we can test c&amp;s interoperability\n
7820       using iCalendar and other IETF standards.
7821      LOCATION:LDB Lobby
7822      ATTACH;FMTTYPE=application/postscript:ftp://xyzCorp.com/pub/
7823       conf/bkgrnd.ps
7824      END:VEVENT
7825      END:VCALENDAR
7826
7827    The following is an example of a to-do due on April 15, 1998. An
7828    audio alarm has been specified to remind the calendar user at noon,
7829    the day before the to-do is expected to be completed and repeat
7830    hourly, four additional times. The to-do definition has been modified
7831    twice since it was initially created.
7832
7833      BEGIN:VCALENDAR
7834      VERSION:2.0
7835      PRODID:-//ABC Corporation//NONSGML My Product//EN
7836      BEGIN:VTODO
7837      DTSTAMP:19980130T134500Z
7838      SEQUENCE:2
7839      UID:uid4@host1.com
7840      ORGANIZER:MAILTO:unclesam@us.gov
7841      ATTENDEE;PARTSTAT=ACCEPTED:MAILTO:jqpublic@host.com
7842
7843
7844
7845 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 138]</span>
7846 </pre><pre class="newpage"><a name="page-139" id="page-139" href="#page-139" class="invisible"> </a>
7847 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7848
7849
7850      DUE:19980415T235959
7851      STATUS:NEEDS-ACTION
7852      SUMMARY:Submit Income Taxes
7853      BEGIN:VALARM
7854      ACTION:AUDIO
7855      TRIGGER:19980403T120000
7856      ATTACH;FMTTYPE=audio/basic:http://host.com/pub/audio-
7857       files/ssbanner.aud
7858      REPEAT:4
7859      DURATION:PT1H
7860      END:VALARM
7861      END:VTODO
7862      END:VCALENDAR
7863
7864    The following is an example of a journal entry.
7865
7866      BEGIN:VCALENDAR
7867      VERSION:2.0
7868      PRODID:-//ABC Corporation//NONSGML My Product//EN
7869      BEGIN:VJOURNAL
7870      DTSTAMP:19970324T120000Z
7871      UID:uid5@host1.com
7872      ORGANIZER:MAILTO:jsmith@host.com
7873      STATUS:DRAFT
7874      CLASS:PUBLIC
7875      CATEGORY:Project Report, XYZ, Weekly Meeting
7876      DESCRIPTION:Project xyz Review Meeting Minutes\n
7877       Agenda\n1. Review of project version 1.0 requirements.\n2.
7878      Definition
7879       of project processes.\n3. Review of project schedule.\n
7880       Participants: John Smith, Jane Doe, Jim Dandy\n-It was
7881        decided that the requirements need to be signed off by
7882        product marketing.\n-Project processes were accepted.\n
7883       -Project schedule needs to account for scheduled holidays
7884        and employee vacation time. Check with HR for specific
7885        dates.\n-New schedule will be distributed by Friday.\n-
7886       Next weeks meeting is cancelled. No meeting until 3/23.
7887      END:VJOURNAL
7888      END:VCALENDAR
7889
7890    The following is an example of published busy time information. The
7891    iCalendar object might be placed in the network resource
7892    www.host.com/calendar/busytime/jsmith.ifb.
7893
7894      BEGIN:VCALENDAR
7895      VERSION:2.0
7896      PRODID:-//RDU Software//NONSGML HandCal//EN
7897      BEGIN:VFREEBUSY
7898
7899
7900
7901 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 139]</span>
7902 </pre><pre class="newpage"><a name="page-140" id="page-140" href="#page-140" class="invisible"> </a>
7903 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7904
7905
7906      ORGANIZER:MAILTO:jsmith@host.com
7907      DTSTART:19980313T141711Z
7908      DTEND:19980410T141711Z
7909      FREEBUSY:19980314T233000Z/19980315T003000Z
7910      FREEBUSY:19980316T153000Z/19980316T163000Z
7911      FREEBUSY:19980318T030000Z/19980318T040000Z
7912      URL:http://www.host.com/calendar/busytime/jsmith.ifb
7913      END:VFREEBUSY
7914      END:VCALENDAR
7915
7916 <span class="h2"><h2><a name="section-6">6</a> Recommended Practices</h2></span>
7917
7918    These recommended practices should be followed in order to assure
7919    consistent handling of the following cases for an iCalendar object.
7920
7921    1.  Content lines longer than 75 octets SHOULD be folded.
7922
7923    2.  A calendar entry with a "DTSTART" property but no "DTEND"
7924        property does not take up any time. It is intended to represent
7925        an event that is associated with a given calendar date and time
7926        of day, such as an anniversary. Since the event does not take up
7927        any time, it MUST NOT be used to record busy time no matter what
7928        the value for the "TRANSP" property.
7929
7930    3.  When the "DTSTART" and "DTEND", for "VEVENT", "VJOURNAL" and
7931        "VFREEBUSY" calendar components, and "DTSTART" and "DUE", for
7932        "VTODO" calendar components, have the same value data type (e.g.,
7933        DATE-TIME), they SHOULD specify values in the same time format
7934        (e.g., UTC time format).
7935
7936    4.  When the combination of the "RRULE" and "RDATE" properties on an
7937        iCalendar object produces multiple instances having the same
7938        start date/time, they should be collapsed to, and considered as,
7939        a single instance.
7940
7941    5.  When a calendar user receives multiple requests for the same
7942        calendar component (e.g., REQUEST for a "VEVENT" calendar
7943        component) as a result of being on multiple mailing lists
7944        specified by "ATTENDEE" properties in the request, they SHOULD
7945        respond to only one of the requests. The calendar user SHOULD
7946        also specify (using the "MEMBER" parameter of the "ATTENDEE"
7947        property) which mailing list they are a member of.
7948
7949    6.  An implementation can truncate a "SUMMARY" property value to 255
7950        characters.
7951
7952
7953
7954
7955
7956
7957 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 140]</span>
7958 </pre><pre class="newpage"><a name="page-141" id="page-141" href="#page-141" class="invisible"> </a>
7959 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
7960
7961
7962    7.  If seconds of the minute are not supported by an implementation,
7963        then a value of "00" SHOULD be specified for the seconds
7964        component in a time value.
7965
7966    8.  If the value type parameter (VALUE=) contains an unknown value
7967        type, it SHOULD be treated as TEXT.
7968
7969    9.  TZURL values SHOULD NOT be specified as a FILE URI type. This URI
7970        form can be useful within an organization, but is problematic in
7971        the Internet.
7972
7973    10.  Some possible English values for CATEGORIES property include
7974         "ANNIVERSARY", "APPOINTMENT", "BUSINESS", "EDUCATION",
7975         "HOLIDAY", "MEETING", "MISCELLANEOUS", "NON-WORKING HOURS", "NOT
7976         IN OFFICE", "PERSONAL", "PHONE CALL", "SICK DAY", "SPECIAL
7977         OCCASION", "TRAVEL", "VACATION". Categories can be specified in
7978         any registered language.
7979
7980    11.  Some possible English values for RESOURCES property include
7981         "CATERING", "CHAIRS", "COMPUTER PROJECTOR", "EASEL", "OVERHEAD
7982         PROJECTOR", "SPEAKER PHONE", "TABLE", "TV", "VCR", "VIDEO
7983         PHONE", "VEHICLE". Resources can be specified in any registered
7984         language.
7985
7986 <span class="h2"><h2><a name="section-7">7</a> Registration of Content Type Elements</h2></span>
7987
7988    This section provides the process for registration of MIME
7989    Calendaring and Scheduling Content Type iCalendar object methods and
7990    new or modified properties.
7991
7992 <span class="h3"><h3><a name="section-7.1">7.1</a> Registration of New and Modified iCalendar Object Methods</h3></span>
7993
7994    New MIME Calendaring and Scheduling Content Type iCalendar object
7995    methods are registered by the publication of an IETF Request for
7996    Comments (RFC). Changes to an iCalendar object method are registered
7997    by the publication of a revision of the RFC defining the method.
7998
7999 <span class="h3"><h3><a name="section-7.2">7.2</a> Registration of New Properties</h3></span>
8000
8001    This section defines procedures by which new properties or enumerated
8002    property values for the MIME Calendaring and Scheduling Content Type
8003    can be registered with the IANA. Non-IANA properties can be used by
8004    bilateral agreement, provided the associated properties names follow
8005    the "X-" convention.
8006
8007    The procedures defined here are designed to allow public comment and
8008    review of new properties, while posing only a small impediment to the
8009    definition of new properties.
8010
8011
8012
8013 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 141]</span>
8014 </pre><pre class="newpage"><a name="page-142" id="page-142" href="#page-142" class="invisible"> </a>
8015 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
8016
8017
8018    Registration of a new property is accomplished by the following
8019    steps.
8020
8021 <span class="h4"><h4><a name="section-7.2.1">7.2.1</a> Define the property</h4></span>
8022
8023    A property is defined by completing the following template.
8024
8025      To: ietf-calendar@imc.org
8026
8027      Subject: Registration of text/calendar MIME property XXX
8028
8029      Property name:
8030
8031      Property purpose:
8032
8033      Property value type(s):
8034
8035      Property parameter (s):
8036
8037      Conformance:
8038
8039      Description:
8040
8041      Format definition:
8042
8043      Examples:
8044
8045    The meaning of each field in the template is as follows.
8046
8047    Property name: The name of the property, as it will appear in the
8048    body of an text/calendar MIME Content-Type "property: value" line to
8049    the left of the colon ":".
8050
8051    Property purpose: The purpose of the property (e.g., to indicate a
8052    delegate for the event or to-do, etc.). Give a short but clear
8053    description.
8054
8055    Property value type (s): Any of the valid value types for the
8056    property value needs to be specified. The default value type also
8057    needs to be specified. If a new value type is specified, it needs to
8058    be declared in this section.
8059
8060    Property parameter (s): Any of the valid property parameters for the
8061    property needs to be specified.
8062
8063    Conformance: The calendar components that the property can appear in
8064    needs to be specified.
8065
8066
8067
8068
8069 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 142]</span>
8070 </pre><pre class="newpage"><a name="page-143" id="page-143" href="#page-143" class="invisible"> </a>
8071 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
8072
8073
8074    Description: Any special notes about the property, how it is to be
8075    used, etc.
8076
8077    Format definition: The ABNF for the property definition needs to be
8078    specified.
8079
8080    Examples: One or more examples of instances of the property needs to
8081    be specified.
8082
8083 <span class="h4"><h4><a name="section-7.2.2">7.2.2</a> Post the Property definition</h4></span>
8084
8085    The property description MUST be posted to the new property
8086    discussion list, ietf-calendar@imc.org.
8087
8088 <span class="h4"><h4><a name="section-7.2.3">7.2.3</a>   Allow a comment period</h4></span>
8089
8090    Discussion on the new property MUST be allowed to take place on the
8091    list for a minimum of two weeks. Consensus MUST be reached on the
8092    property before proceeding to the next step.
8093
8094 <span class="h4"><h4><a name="section-7.2.4">7.2.4</a> Submit the property for approval</h4></span>
8095
8096    Once the two-week comment period has elapsed, and the proposer is
8097    convinced consensus has been reached on the property, the
8098    registration application should be submitted to the Method Reviewer
8099    for approval. The Method Reviewer is appointed to the Application
8100    Area Directors and can either accept or reject the property
8101    registration. An accepted registration should be passed on by the
8102    Method Reviewer to the IANA for inclusion in the official IANA method
8103    registry. The registration can be rejected for any of the following
8104    reasons. 1) Insufficient comment period; 2) Consensus not reached; 3)
8105    Technical deficiencies raised on the list or elsewhere have not been
8106    addressed. The Method Reviewer's decision to reject a property can be
8107    appealed by the proposer to the IESG, or the objections raised can be
8108    addressed by the proposer and the property resubmitted.
8109
8110 <span class="h3"><h3><a name="section-7.3">7.3</a> Property Change Control</h3></span>
8111
8112    Existing properties can be changed using the same process by which
8113    they were registered.
8114
8115         1.           Define the change
8116
8117         2.           Post the change
8118
8119         3.           Allow a comment period
8120
8121         4.           Submit the property for approval
8122
8123
8124
8125 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 143]</span>
8126 </pre><pre class="newpage"><a name="page-144" id="page-144" href="#page-144" class="invisible"> </a>
8127 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
8128
8129
8130    Note that the original author or any other interested party can
8131    propose a change to an existing property, but that such changes
8132    should only be proposed when there are serious omissions or errors in
8133    the published memo. The Method Reviewer can object to a change if it
8134    is not backward compatible, but is not required to do so.
8135
8136    Property definitions can never be deleted from the IANA registry, but
8137    properties which are no longer believed to be useful can be declared
8138    OBSOLETE by a change to their "intended use" field.
8139
8140 <span class="h2"><h2><a name="section-8">8</a> References</h2></span>
8141
8142    [<a name="ref-IMIP" id="ref-IMIP">IMIP</a>]     Dawson, F., Mansour, S. and S. Silverberg, "iCalendar
8143               Message-based Interoperability Protocol (IMIP)", <a href="http://tools.ietf.org/html/rfc2447">RFC 2447</a>,
8144               November 1998.
8145
8146    [<a name="ref-ITIP" id="ref-ITIP">ITIP</a>]     Silverberg, S., Mansour, S., Dawson, F. and R. Hopson,
8147               "iCalendar Transport-Independent Interoperability Protocol
8148               (iTIP) : Scheduling Events, Busy Time, To-dos and Journal
8149               Entries", <a href="http://tools.ietf.org/html/rfc2446">RFC 2446</a>, November 1998.
8150
8151    [ISO 8601] ISO 8601, "Data elements and interchange formats-
8152               Information interchange--Representation of dates and
8153               times", International Organization for Standardization,
8154               June, 1988.
8155
8156    [ISO 9070] ISO/IEC 9070, "Information Technology_SGML Support
8157               Facilities--Registration Procedures for Public Text Owner
8158               Identifiers", Second Edition, International Organization
8159               for Standardization, April 1991.
8160
8161    [<a name="ref-RFC 822" id="ref-RFC 822">RFC 822</a>]  Crocker, D., "Standard for the Format of ARPA Internet
8162               Text Messages", STD 11, <a href="http://tools.ietf.org/html/rfc822">RFC 822</a>, August 1982.
8163
8164    [<a name="ref-RFC 1738" id="ref-RFC 1738">RFC 1738</a>] Berners-Lee, T., Masinter, L. and M. McCahill, "Uniform
8165               Resource Locators (URL)", <a href="http://tools.ietf.org/html/rfc1738">RFC 1738</a>, December 1994.
8166
8167    [<a name="ref-RFC 1766" id="ref-RFC 1766">RFC 1766</a>] Alvestrand, H., "Tags for the Identification of
8168               Languages", <a href="http://tools.ietf.org/html/rfc1766">RFC 1766</a>, March 1995.
8169
8170    [<a name="ref-RFC 2045" id="ref-RFC 2045">RFC 2045</a>] Freed, N. and N. Borenstein, " Multipurpose Internet Mail
8171               Extensions (MIME) - Part One: Format of Internet Message
8172               Bodies", <a href="http://tools.ietf.org/html/rfc2045">RFC 2045</a>, November 1996.
8173
8174    [<a name="ref-RFC 2046" id="ref-RFC 2046">RFC 2046</a>] Freed, N. and N. Borenstein, " Multipurpose Internet Mail
8175               Extensions (MIME) - Part Two: Media Types", <a href="http://tools.ietf.org/html/rfc2046">RFC 2046</a>,
8176               November 1996.
8177
8178
8179
8180
8181 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 144]</span>
8182 </pre><pre class="newpage"><a name="page-145" id="page-145" href="#page-145" class="invisible"> </a>
8183 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
8184
8185
8186    [<a name="ref-RFC 2048" id="ref-RFC 2048">RFC 2048</a>] Freed, N., Klensin, J. and J. Postel, "Multipurpose
8187               Internet Mail Extensions (MIME) - Part Four: Registration
8188               Procedures", <a href="http://tools.ietf.org/html/rfc2048">RFC 2048</a>, January 1997.
8189
8190    [<a name="ref-RFC 2119" id="ref-RFC 2119">RFC 2119</a>] Bradner, S., "Key words for use in RFCs to Indicate
8191               Requirement Levels", <a href="http://tools.ietf.org/html/bcp14">BCP 14</a>, <a href="http://tools.ietf.org/html/rfc2119">RFC 2119</a>, March 1997.
8192
8193    [<a name="ref-RFC 2234" id="ref-RFC 2234">RFC 2234</a>] Crocker, D. and P. Overell, "Augmented BNF for Syntax
8194               Specifications: ABNF", <a href="http://tools.ietf.org/html/rfc2234">RFC 2234</a>, November 1997.
8195
8196    [<a name="ref-RFC 2279" id="ref-RFC 2279">RFC 2279</a>] Yergeau, F., "UTF-8, a transformation format of ISO
8197               10646", <a href="http://tools.ietf.org/html/rfc2279">RFC 2279</a>, January 1998.
8198
8199    [<a name="ref-RFC 2425" id="ref-RFC 2425">RFC 2425</a>] Howes, T., Smith, M. and F. Dawson, "A MIME Content-Type
8200               for Directory Information", <a href="http://tools.ietf.org/html/rfc2425">RFC 2425</a>, September 1998.
8201
8202    [<a name="ref-RFC 2426" id="ref-RFC 2426">RFC 2426</a>] Dawson, F. and T. Howes, "vCard MIME Directory Profile",
8203               <a href="http://tools.ietf.org/html/rfc2426">RFC 2426</a>, September 1998.
8204
8205    [<a name="ref-TZ" id="ref-TZ">TZ</a>]       Olson, A.D., et al, Time zone code and data,
8206               <a href="ftp://elsie.nci.nih.gov/pub/">ftp://elsie.nci.nih.gov/pub/</a>, updated periodically.
8207
8208    [<a name="ref-VCAL" id="ref-VCAL">VCAL</a>]     Internet Mail Consortium, "vCalendar - The Electronic
8209               Calendaring and Scheduling Exchange Format",
8210               <a href="http://www.imc.org/pdi/vcal-10.txt">http://www.imc.org/pdi/vcal-10.txt</a>, September 18, 1996.
8211
8212 <span class="h2"><h2><a name="section-9">9</a> Acknowledgments</h2></span>
8213
8214    A hearty thanks to the IETF Calendaring and Scheduling Working Group
8215    and also the following individuals who have participated in the
8216    drafting, review and discussion of this memo:
8217
8218    Roland Alden, Harald T. Alvestrand, Eric Berman, Denis Bigorgne, John
8219    Binici, Bill Bliss, Philippe Boucher, Steve Carter, Andre
8220    Courtemanche, Dave Crocker, David Curley, Alec Dun, John Evans, Ross
8221    Finlayson, Randell Flint, Ned Freed, Patrik Faltstrom, Chuck
8222    Grandgent, Mark Handley, Steve Hanna, Paul B. Hill, Paul Hoffman,
8223    Ross Hopson, Mark Horton, Daryl Huff, Bruce Kahn, C. Harald Koch,
8224    Ryan Jansen, Don Lavange, Antoine Leca, Theodore Lorek, Steve
8225    Mansour, Skip Montanaro, Keith Moore, Cecil Murray, Chris Newman,
8226    John Noerenberg, Ralph Patterson, Pete Resnick, Keith Rhodes, Robert
8227    Ripberger, John Rose, Doug Royer, Andras Salamar, Ted Schuh, Vinod
8228    Seraphin, Derrick Shadel, Ken Shan, Andrew Shuman, Steve Silverberg,
8229    William P. Spencer, John Sun, Mark Towfiq, Yvonne Tso, Robert Visnov,
8230    James L. Weiner, Mike Weston, William Wyatt.
8231
8232
8233
8234
8235
8236
8237 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 145]</span>
8238 </pre><pre class="newpage"><a name="page-146" id="page-146" href="#page-146" class="invisible"> </a>
8239 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
8240
8241
8242 <span class="h2"><h2><a name="section-10">10</a> Authors' and Chairs' Addresses</h2></span>
8243
8244    The following address information is provided in a MIME-VCARD,
8245    Electronic Business Card, format.
8246
8247    The authors of this memo are:
8248
8249    BEGIN:VCARD
8250    VERSION:3.0
8251    N:Dawson;Frank
8252    FN:Frank Dawson
8253    ORG:Lotus Development Corporation
8254    ADR;TYPE=WORK,POSTAL,PARCEL:;;6544 Battleford Drive;
8255     Raleigh;NC;27613-3502;USA
8256    TEL;TYPE=WORK,MSG:+1-919-676-9515
8257    TEL;TYPE=WORK,FAX:+1-919-676-9564
8258    EMAIL;TYPE=PREF,INTERNET:Frank_Dawson@Lotus.com
8259    EMAIL;TYPE=INTERNET:fdawson@earthlink.net
8260    URL:http://home.earthlink.net/~fdawson
8261    END:VCARD
8262
8263    BEGIN:VCARD
8264    VERSION:3.0
8265    N:Stenerson;Derik
8266    FN:Derik Stenerson
8267    ORG:Microsoft Corporation
8268    ADR;TYPE=WORK,POSTAL,PARCEL:;;One Microsoft Way;
8269     Redmond;WA;98052-6399;USA
8270    TEL;TYPE=WORK,MSG:+1-425-936-5522
8271    TEL;TYPE=WORK,FAX:+1-425-936-7329
8272    EMAIL;TYPE=INTERNET:deriks@Microsoft.com
8273    END:VCARD
8274
8275    The iCalendar object is a result of the work of the Internet
8276    Engineering Task Force Calendaring and Scheduling Working Group. The
8277    chairmen of that working group are:
8278
8279    BEGIN:VCARD
8280    VERSION:3.0
8281    N:Ganguly;Anik
8282    FN:Anik Ganguly
8283    ORG: Open Text Inc.
8284    ADR;TYPE=WORK,POSTAL,PARCEL:;Suite 101;38777 West Six Mile Road;
8285     Livonia;MI;48152;USA
8286    TEL;TYPE=WORK,MSG:+1-734-542-5955
8287    EMAIL;TYPE=INTERNET:ganguly@acm.org
8288    END:VCARD
8289
8290
8291
8292
8293 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 146]</span>
8294 </pre><pre class="newpage"><a name="page-147" id="page-147" href="#page-147" class="invisible"> </a>
8295 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
8296
8297
8298    The co-chairman of that working group is:
8299
8300    BEGIN:VCARD
8301    VERSION:3.0
8302    N:Moskowitz;Robert
8303    FN:Robert Moskowitz
8304    EMAIL;TYPE=INTERNET:rgm-ietf@htt-consult.com
8305    END:VCARD
8306
8307
8308
8309
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8348
8349 <span class="grey">Dawson &amp; Stenerson          Standards Track                   [Page 147]</span>
8350 </pre><pre class="newpage"><a name="page-148" id="page-148" href="#page-148" class="invisible"> </a>
8351 <span class="grey"><a href="http://tools.ietf.org/html/rfc2445">RFC 2445</a>                       iCalendar                   November 1998</span>
8352
8353
8354 <span class="h2"><h2><a name="section-11">11</a>.  Full Copyright Statement</h2></span>
8355
8356    Copyright (C) The Internet Society (1998).  All Rights Reserved.
8357
8358    This document and translations of it may be copied and furnished to
8359    others, and derivative works that comment on or otherwise explain it
8360    or assist in its implementation may be prepared, copied, published
8361    and distributed, in whole or in part, without restriction of any
8362    kind, provided that the above copyright notice and this paragraph are
8363    included on all such copies and derivative works.  However, this
8364    document itself may not be modified in any way, such as by removing
8365    the copyright notice or references to the Internet Society or other
8366    Internet organizations, except as needed for the purpose of
8367    developing Internet standards in which case the procedures for
8368    copyrights defined in the Internet Standards process must be
8369    followed, or as required to translate it into languages other than
8370    English.
8371
8372    The limited permissions granted above are perpetual and will not be
8373    revoked by the Internet Society or its successors or assigns.
8374
8375    This document and the information contained herein is provided on an
8376    "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
8377    TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
8378    BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
8379    HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
8380    MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
8381
8382
8383
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8404
8405 Dawson &amp; Stenerson          Standards Track                   [Page 148]
8406 </pre><pre class="newpage">
8407 </pre><br>
8408 <span class="noprint"><small><small>Html markup produced by rfcmarkup 1.74, available from
8409 <a href="http://tools.ietf.org/tools/rfcmarkup/">http://tools.ietf.org/tools/rfcmarkup/</a>
8410 </small></small></span>
8411 </body></html>