A unique identifier for the calendar.
- iOS 5.0+
- macOS 10.8+
- Mac Catalyst 13.0+
- watchOS 2.0+
This property is set when the calendar is created and can be used as a local identifier. Use
calendar(with to get a calendar with the specified identifier.
A full sync with the calendar will lose this identifier. You should have a plan for dealing with a calendar whose identifier is no longer fetch-able by caching its other properties.