The Living Daylights

Last weekend, I was doing some research work on a computing cluster in Germany, and the time stamps suddenly jumped by an hour – Turns out the EU changes from daylight saving time on the last Sunday of October, rather than the first Sunday of November.  I had been under the impression (along with many others) that DST was introduced for the benefit of farmers, but they actually lobbied against it.  The original intent was to give more daylight after the work day, to encourage people to shop.  I thought I'd take a look at how this idea lines up with the sunrise/set times from the US Naval Observatory.  Here are the times using standard time all year:

The black lines show my usual wake/sleep times.  Now if we introduce DST:

By using DST, I'm awake during more of the daylight.  This is the rationale behind one of the other arguments for changing clocks – energy savings by reducing light/heat use.  It's easier to see if we look at the overlap between waking and daylight in the two systems:

The idea that DST saves energy is disputed though, and a number of studies have not shown a conclusive benefit, so it's likely a small effect if any.  Seems likely to stay though, since getting rid of DST would take more effort than it costs to keep around.  I'll just have to keep a close eye on my foreign time stamps.