Every spring in the northern hemisphere about 1.6 billion people have to change their clocks as they move into daylight saving time. For many, including Europeans this week (Australians will be doing the opposite on Sunday), the joys of the season include a sleep-deprived few days after the clocks change and having to explain to children bouncing off the walls that, despite the bright daylight outside, it is in fact bedtime.

The origin of daylight saving lies in efforts to use less energy in wartime, by having more sunshine in the evening. But the evidence suggests that the costs are surprisingly large, not just because of the immediate disruption to people’s daily lives, but also because of the longer-term biological consequences of moving out of sync with the sun.

The Economist