Actually this isn't a totally trivial question. The time zones in calendar appointments can change, if there's a switch between standard time and summer time.

Actually this isn't a totally trivial question. The time zones in calendar appointments can change, if there's a switch between standard time and summer time. You need to know when is the hour set back by 1 hour, and in that case sometimes the answer is ,,maybe''. I was working at a small phone company, and handling the switch between time zones were not just non-trivial, but they caused hard-to find bugs, as these things happen only twice a year.