Is it the user's time zone, the time zone of the affected party (such as a remote office or process), or an arbitrary time zone standard, such as UTC (Coordinated Universal time)?

There sits Newfoundland, which has its own time zone (NST: Newfoundland Standard Time), three and a half hours behind Greenwich Mean Time and half an hour ahead of eastern mainland Canada.

November 2, 1868, time zone: New Zealand officially adopts a standard time to be observed nationally.