web calendars
iCalendar is a standard (RFC 2445) 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. 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.