The Pattern appointment defines a recurring series, and Occurrence appointments are generated automatically according to the pattern. If you modify an occurrence (for example, postpone it for an hour), its type changes to ChangedOccurrence. If you delete an occurrence, it becomes a DeletedOccurrence.
If you modify the pattern, the Scheduler removes all changed and deleted occurrences and repopulates the series with regular occurrences.
How to Access Occurrences and Exceptions
The Pattern, ChangedOccurrence, and DeletedOccurrence appointments are stored in the SchedulerControl.AppointmentItems collection. The Occurrence appointments are not stored in any collection to avoid a stack overflow for infinite recurring series. These appointments are automatically generated at runtime based on the pattern's AppointmentItem.RecurrenceInfo.