Recent Bus Departure

Make time semantics explicit

Ask whether departures are one-time timestamps or recurring schedules, which time zone applies, whether the current moment is included, and whether the desired answer is the latest departure at or before now or the nearest departure in either direction. Normalize all times to a single absolute representation such as UTC instants before comparison. For a static sorted list, binary-search the rightmost departure <= now; that is O(log n) query time after O(n log n) sorting and O(n) storage. For a stream, maintain an ordered index or update the latest eligible value as events arrive. Test an exact-time departure, no past departure, midnight and daylight-saving boundaries, duplicate timestamps, and stale schedule data. Never compare formatted local-time strings when zones can differ.