Well, as it happens I've spent all day trying to get some software for time zones working. It's hellishly complicated, you know, and not helped by the way there are acronyms for some bits (GMT, UTC, etc) but not for others (there's no agreed acronym for 'UK Time' for example, which is GMT part of the year and BST for others; the same lack of a name seems to apply to most, but not all, 'variable' zones); nor is it helpful when two completely separate parts of the world both want to refer to EST (US and Australia.) Just to add to the amusement, Microsoft's TimeZoneInfo facilities do something completely bizarre when the time is ambiguous (i.e. the ambiguity is resolved differently for "what's the time?" and "Is there daylight saving?"

Then there's a whole political layer when the same timezone (in terms of UTC offset) needs to have different names in different places to avoid upsetting people ...