This specification introduces the hCalendar format, which is a 1:1 representation of the iCalendar standard, in semantic XHTML.
GCALDaemon is an OS-independent Java program that offers two-way synchronization between Google Calendar and various iCalalendar compatible calendar applications.
GridCalendar (abbreviated as grical), is an open web where people store quickly a few information about interesting events, so that others can also easily know about them. Grical makes easy and fast for its users to get notified and store interesting events in its own external calendars.
apples caldav calendar server in python
Giggity is an Android app that loads xcal/Pentabarf XML files (that contain schedules of conferences/festivals/other events) and lets you browse them in various convenient formats.
Schulferien und weitere iCal (.ics) Kalender
