public JwTimestamp InferActualDepartureFromActualArrival(JwTimestamp actualArrival)
 {
     JwTimestamp ts = actualArrival.GetTimestampCopy();
     ts.AddDuration(GetTimezoneOffset());
     ts.SubtractDuration(GetTransitDuration());
     return ts;
 }
 public JwTimestamp ComputeScheduledDepartureLocalTimestampFromScheduledArrival(JwTimestamp scheduledArrivalTs)
 {
     JwTimestamp ts = scheduledArrivalTs.GetTimestampCopy();
     ts.SubtractDuration( GetTransitDuration());
     ts.SubtractDuration( GetTimezoneOffset());
     return ts;
 }