iCalendar

A standard for group calendaring and scheduling from the IETF. It enables calendaring data to be sent via e-mail or the Web that is automatically entered into the recipient's schedule. In addition a request for a meeting with free and busy times could be sent, and the recipient's software could book the time automatically and send back the response.

The Successor to vCalendar
iCalendar superseded the vCalendar standard originally developed by Versit, then turned over to the Internet Mail Consortium (IMC) and later the IETF. It added more detail to the vCalendar events and defined a protocol for transporting it. iCalendar was proposed as a universal standard to replace proprietary specifications such as in Outlook/Exchange, Lotus Notes and Groupwise, but this has not occurred.

Dubbed "calsify," the IETF Calendaring and Scheduling Standards Simplification group works on interoperability between different scheduling systems.