Defines a Date or DateTime during which a scheduled Event will not take place. The property allows exceptions to a Schedule to be specified. If an exception is specified as a DateTime then only the event that would have started at that specific date and time should be excluded from the schedule. If an exception is specified as a Date then any event that is scheduled for that 24 hour period should be excluded from the schedule. This allows a whole day to be excluded from the schedule without having to itemise every scheduled event.