CalDAV
Exchange ActiveSync
Comparison of CalDAV and CardDAV implementations
Calendar
CardDAV
GroupDAV, an effort to create a simplified, straightforward protocol for calendars as well as contacts.
iCalendar
Scheduling OSID defines a software interface abstraction for calendaring protocols.
SyncML
vCalendar
WebDAV
https://ja.wikipedia.org/wiki/CalDAV
https://en.wikipedia.org/wiki/CalDAV