Calendar Server automatically creates a default calendar for a user the first time the user logs in. This feature is called auto-provisioning. Autoprovisioning is enabled by default. However, auto-provisioning is available for user calendars only; resource calendars must be explicitly created.
Calendar Server creates the calendar ID (calid) for this new default calendar from the user ID, unless a calendar by that name already exists.
For example, if John Smith, with a user ID of jsmith, logs into Calendar Server for the first time, Calendar Server automatically creates a default calendar with jsmith as the calid. Each subsequent calendar John Smith creates has a calid with jsmith: prepended to the calendar name. For example, if John Smith later creates a new calendar named meetings, the calid for the new calendar (in a non-hosted environment) is jsmith:meetings.
Calendar Server returns the Calendar not found error when a user without a default calendar is specified as an attendee.