Don't forget the Americans: A few years ago, the duration of US Daylight Saving Time was changed to have longer duration (It used to be early April to late October; now it's late May to early November). I'm sure that even now there are a few people here with the opposite problem: They remember to change their clocks back, but they do it a week early.

Yes, I remember getting lots of email at the time asking me strange questions like 'Is PuTTY DST compliant?'. Almost nobody bothered to explain that 'DST compliant' meant 'compliant with a recent change of DST policy in a particular country you don't inhabit', but fortunately one or two people did...