Comment by graemep

That is a good point, but fortunately a rare case.

The other problem is that when you are using human inputs such as appointments you may not know which is appropriate. If I arrange a meeting with someone in another timezone, and there is such a change, how can a system know whether I want the UTC time, my timezone, or the other person's timezone.

I am not sure there is a good way to do this in many cases. As you say some culturally defined times are definitely tied to the local timezone, but a lot of things will not be. There is a loss of information, but that information may not be useful on many cases.

I think I agree with you in that there is no universal solution. However, store UTC is probably good enough a lot of the time. In general, timezone changes would be announced well ahead of time so UTC would be fine except for times fixed far ahead.

I have actually lived through timezone changes that were decided on in emergency circumstances (Sri Lanka faced with a severe electricity shortage) and the result was chaos. People genuinely did not know whether an appointment would take place in "old time" or "new time"! No system devised earlier could have coped with that because intent was no unambiguous.