2010-03-28
Changing Clocks
Today Europe changed its clocks for daylight saving time, two weeks after the US did. I’m not going to take part in the twice-a-year ritual of suggesting that the UK should move a further hour ahead, or the counter-complaints that changing clocks is silly. Instead, I’m going to praise the way Europeans change their clocks, and criticise the way Americans do.
The core of the question is, when do you actually change the clocks? Obviously, doing so during the night is the right answer, but the European scheme is subtly better: everyone changes their clocks forward and back at 0100 GMT. By contrast, the American scheme has the change happening at 0100 local time.
Why’s the European scheme better? It means it’s obvious what time it is everywhere, at the (smallish) cost of making the local time for each change different. As an example, let’s say it’s 2:30 GMT this morning in Berlin; half an hour after the clocks have gone forward. The local time is now 3:30 CEDT; in Helsinki, it’s 4:30, and in London, 2:30 BST.
Contrast that with the time in Chicago, at 3.30 am on the morning the US enters daylight savings time. It’s easy to find the time in New York: it’s an hour ahead, at 4:30 am. In San Francisco, though, it’s not the usual two hours behind, but three, at half past midnight; they won’t enter DST for another hour and a half. Instead of the clocks all moving forward, there’s a wave of confusion.
Now, I’ll admit it’s easier for Europe to do this. It only spans three time zones, whereas the continental US spans four, and including Alaska and Newfoundland, six (although the latter is only a half-hour). Making the change simultaneous would mean that, say, Juneau would have a local change at midnight while in St. John’s the change would be as late as half past five in the morning.
Easy or not, though, I prefer the European approach. It’s certainly easy to code around.
