Internet standard defined in
RFCs
2445,
2446 and
2447. Specified by
Internet Mail Consortium.
vCalendar format is basically a calendar format that was designed to make interchange between different calendar and scheduling programs easier. It is an open standard, and also has commercial support.
Some programs that support vCalendar include GNOME Calendar, Ximian Evolution and korganizer.
See also: vCard.