iCalendar

iCalendar is a standard for calendar data exchange. The standard is sometimes referred to as "iCal", which also is the name of the Apple, Inc. calendar program (see iCal) that provides one of the implementations of the standard.

iCalendar allows users to send meeting requests and tasks to other users through email. Recipients of the iCalendar email (with supported software) can respond to the sender easily or counter propose another meeting date/time.

It is implemented/supported by a large number of products, including 37signals Backpack, 30 Boxes, Apple's iCal application, Darwin Calendar Server, Contactizer and iPod. Buni Meldware Communication Suite, Chandler, Drupal with its event module, TYPO3 via its Calendar Base Extension, Citadel, Facebook, FirstClass, Google Calendar, Horde, Jalios JCMS, Joyent Connector, KOrganizer, Lotus Notes, Microsoft Entourage, Microsoft Exchange, Mozilla Calendar (including Mozilla Sunbird and Lightning), Mulberry, Novell Evolution, Novell GroupWise, Nuvvo, Simple Groupware, SOHO Organizer, Sun Java Calendar Server, Upcoming.org, Windows Calendar, Microsoft Works Calendar, Webical, Zimbra Collaboration Suite, and, in its latest version of the software, Microsoft Outlook, BlackBerry, Internet edition from v2.3 onwards now recognizes iCalendar and iCalendar invites can be sent and received with the Blackberry Server. Notably missing from this list is the Palm Desktop, Palm (PDA), and Now-Up-To-Date.

iCalendar data is typically exchanged using traditional email, but the standard is designed to be independent of the transport protocol. For example, it can also be shared and edited by using a WebDav server, or SyncML. Simple web servers (using just the HTTP protocol) are often used to distribute iCalendar data about an event and to publish busy times of an individual. Publishers can embed iCalendar data in web pages using hCalendar, a 1:1 microformat representation of iCalendar in semantic (X)HTML.