iCalendar RFC 2445
iCalendar is a specification maintained by the IETF Calendaring Extensions (calext) Working Group, and is a widely used standard for the storage and exchange of calendar information. It was originally specified, as "vCalendar", by the Versit Consortium, before being passed to the Internet Mail Consortium, and finally adopted by the IETF. The second revision of the standard, renamed to iCalendar, has formed the basis of many calendaring applications for decades. Recent work within the IETF has proposed both new JSON-based syntax, as well as revised and extended semantics.
The core iCalendar objects include: events, todos, journal entries, and supporting timezone data. These definitions formed the semantic basis for the hCalendar microformat.
History
- vCalendar The original vCalendar specification, no longer in significant use.
- RFC 2445, "Internet Calendaring and Scheduling Core Object Specification (iCalendar)", from 1998, defines the iCalendar 2.0 format, the basis for hCalendar.
- RFC 5445, "Internet Calendaring and Scheduling Core Object Specification (iCalendar)", from 2009, updates and replaces RFC 2445.
- RFC 6321, "xCal: The XML Format for iCalendar", from 2011, maps the iCalendar syntax to XML.
- RFC 7265, "jCal: The JSON Format for iCalendar", from 2014, maps the iCalendar syntax to JSON.
- RFC 7529, "Non-Gregorian Recurrence Rules in the Internet Calendaring and Scheduling Core Object Specification (iCalendar)", from 2015, extends iCalendar.
- RFC 7953, "Calendar Availability", from 2016, extends iCalendar with free/busy components for public scheduling.
- RFC 7986, "New Properties for iCalendar", from 2016, extends iCalendar.
- RFC 9074, "'VALARM' Extensions for iCalendar", from 2021, extends iCalendar to support alarms.
- RFC 9253, "Support for iCalendar Relationships", from 2022, extends iCalendar to support relationships between calendar objects.
As of 2025, work in the IETF continues on a revised JSON format (JSCalendar), guidelines for conversion from iCalendar to JSCalendar (potentially valuable for microformats), revisions to tasks, extensions for polling and subscription, and more.
References
When normatively referencing RFC 2445 on this wiki, either do so by linking to this page with:
{{RFC2445}}
or directly to http://www.ietf.org/rfc/rfc2445.txt.
Avoid linking to the informative HTML translation of rfc2445.txt, which you must explicitly do by avoiding simply using the string RFC 2445 in your text, as MediaWiki appears to auto-hyperlink it to the HTML translation thus: RFC 2445.
Validator
- https://icalendar.org/validator.html
- About the validator. (initial version launched in June 2015)