Calendar Server
ces, single-valued
icsCalendarResource, icsCalendarGroup, icsCalendarUser
The calendar ID (calid) of the default calendar for a user, group, or resource. Required attribute. It is a policy of Calendar Server to construct calids based on the user's uid or the group's groupid, since it is guaranteed to be unique.
icsCalendar: jdoe
2.16.840.1.113730.3.1.731