Add a transition to this timetable on the specified date at the specified time having the specified code. If time is already a transition point on date, replace the existing code with code. The addition of a transition, but not the replacement of the code of an existing transition, invalidates all iterators. The behavior is undefined unless 24 > time.hour(), date is within the valid range of this timetable, and 0 <= code || k_UNSET_TRANSITION_CODE == code.