Case 1: Journey start belongs to the previous OperatingDay

The time format consists only of the hour, minutes (and seconds) of a 24-hour clock, e.g. ‘23:55:00’. If a ServiceJourney’s DepartureTime falls after midnight but the journey still belongs to the previous day’s schedule (e.g. the last-mile S1 departing at 00:11, counted as part of yesterday’s service), DepartureDayOffset must be set to 1.

Case 2: Journey crosses midnight during its course

TimeDemandType/TimingLink hold only relative durations (RunTime, WaitTime) — there is no per-stop DayOffset element in this model. Consequently, a midnight crossing partway through a journey is not explicitly flagged anywhere — it follows implicitly from cumulating DepartureTime with the RunTime/WaitTime values of the TimeDemandType. No additional element is needed or available for this case.