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iCalendar.org
 * Home
 * Specifications
   * iCalendar (RFC 5545)
   * New Properties for iCalendar (RFC 7986)
   * iCalendar Venue (Draft)
   * CalDAV Access (RFC 4791)
   * CalDAV Scheduling (RFC 6638)
 * Validator
 * PHP Library
 * RRULE Tool
 * IoT
 * Resources
 * News
 * Contact Us



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WELCOME

Thank you for visiting iCalendar.org.  This site is devoted to promoting the
iCalendar standard, an open standard for exchanging calendar and scheduling
information between users and computers.  On this site you will find iCalendar
resources, an iCalendar validator and specifications for iCalendar and related
protocols in an easy to use layout.

This site was created by Z Content, a developer of iCalendar tools for the
Joomla Content Management System.  It is hoped this site will help foster the
use of iCalendar and open standards.

 

 


ICALENDAR VALIDATOR AVAILABLE

The iCalendar Validator provides developers and testers a method to validate
their iCalendar feeds, which takes data from a URL, file or text snippet and
compares it against the RFC 5545 specification.  We believe we have one of the
best validation tools available on the internet. More information about the
validator can be found here.


THE ICALENDAR STANDARD


INTRODUCTION

iCalendar is a standard method of transferring calendar information between
computer systems. The standard allows products from many vendors to transfer
calendar information between each other.  iCalendar files typically have the
file extension ".ical" ".ics" ".ifb"  or ".icalendar" with a MIME type of
"text/calendar".

The iCalendar open standard should not be confused with iCal, the former name
for the commercial product "Calendar" developed by Apple Computer.


HISTORY

iCalendar was first defined as a standard as RFC 2445 in 1998 by the Internet
Engineering Task Force (IETF). This document was authored by Frank Dawson of
Lotus Notes Corporation (now owned by IBM) and Derik Stenerson of Microsoft
Corporation. The pairing of these two individuals from competing software
companies highlighted the need at that time for companies to work together to
provide interoperability standards between calendar products.  This
interoperability continues to the present day extending support to new
technologies such as web site calendar services, smart phones and tablets.

The iCalendar standard was refined in 2009 as RFC 5545 and edited by Bernard
Desruisseaux of Oracle Corporation. This resolved some ambiguities from the
original standard as well as deprecated a few features that were no longer
needed. RFC 5545 is now considered the iCalendar standard and supersedes the
previous RFC. RFC 7986 was published in 2016 and adds to the original iCalendar
RFC by defining new properties to support conferencing systems and to the main
VCALENDAR object including a calendar name, description and refresh interval.



Today, iCalendar is used to import and synchronize events on various platforms,
including smart phones, computer and web applications.  Web applications include
Microsoft Office 365, Apple Calendar, Google Calendar, and Yahoo Calendar.


ICALENDAR FILE FORMAT

Here is a sample iCalendar file containing a single event.

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//ZContent.net//Zap Calendar 1.0//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
SUMMARY:Abraham Lincoln
UID:c7614cff-3549-4a00-9152-d25cc1fe077d
SEQUENCE:0
STATUS:CONFIRMED
TRANSP:TRANSPARENT
RRULE:FREQ=YEARLY;INTERVAL=1;BYMONTH=2;BYMONTHDAY=12
DTSTART:20080212
DTEND:20080213
DTSTAMP:20150421T141403
CATEGORIES:U.S. Presidents,Civil War People
LOCATION:Hodgenville\, Kentucky
GEO:37.5739497;-85.7399606
DESCRIPTION:Born February 12\, 1809\nSixteenth President (1861-1865)\n\n\n
 \nhttp://AmericanHistoryCalendar.com
URL:http://americanhistorycalendar.com/peoplecalendar/1,328-abraham-lincol
 n
END:VEVENT
END:VCALENDAR


An iCalendar file consists of sections starting with "BEGIN:" and ending with
"END:".  The "VCALENDAR" is the global section that holds all other sections. 
Other sections include "VEVENT" for events, "VTODO" for to-do items, "VJOURNAL"
for journal entries, and "VTIMEZONE" for time zone information.  Multiple
sections of the same type can be repeated.  For example, multiple "VEVENT"
sections can occur in an iCalendar file to describe multiple events.


CALDAV: REMOTE EVENT MANAGEMENT

The WebDAV standard enables editing web sites remotely.  This standard has been
extended to create the CalDAV standard.  Similar to the WebDAV standard, CalDAV
enables the management of events from a remote location.  Calendar clients such
as Mozilla's Sunbird and Apple's Calendar applications allow editing of events
that reside on a remote server.  


EXTENDING THE ICALENDAR STANDARD

Although the iCalendar specification is very detailed and covers many aspects of
calendaring and scheduling, users have found some features lacking in the
standard.  Fortunately, the standard is extensible and provides a method of
adding additional information to an iCalendar data stream.  Since these features
are not part of the standard, support for them will vary from vendor to vendor.
A few of these extensions are listed here.


HTML IN EVENT DESCRIPTIONS

The original iCalendar standard allowed only plain text as part of an event
description.  HTML markup, such as font attributes (bold, underline) and layout
(div, table) was not allowed in the text description field.  First seen in
Microsoft Outlook, the X-ALT-DESC parameter provides a method to add HTML to an
event description.  "X-" fields are allowed for non-standard, experimental
parameters. This field has become the method of choice when including HTML in a
description.  When using HTML, both fields must be included so that iCalendar
readers that do not support the X-ALT-DESC field can still read the text
version.


DETAILED LOCATION/VENUE INFORMATION

The original iCalendar standard provided a single element for a location
description.  This proved inadequate for some who wanted to include additional
information about the location, including address, contact information and a
description of the location.  A draft proposal entitled, "Internet Calendaring
and Scheduling Venue Component Specification" was published in 2007 by Charles
Norris of Eventful.com and Jeff McCullough of the University of California,
Berkley, to address these issues.  Although it was never fully adopted as an
RFC, this document provides a standard method for transferring venue information
where the iCalendar standard is lacking.

 


RECENT NEWS

 * Validator Version 1.15 released
 * New Look for Web Site
 * New Validator Release Provides New Checks, Including an RFC 7986 Check
 * New RRULE Tool Now Available
 * Validator Moves From Beta to Production

This site is maintained by Z Content, a developer of PHP iCalendar tools for the
Joomla Content Management System. It is hoped this site will help foster the use
of iCalendar and open standards.