Why do clocks go back an hour when summer time ends?

In summer the sun rises early and sets late. Moving clocks an hour ahead means that even if you still get up at 7, you start your day an hour earlier by the sun, and you get an extra hour of bright evening after work. The idea of saving electricity for lighting spread widely after Germany first applied it nationwide in 1916, during the First World War. The English name, daylight saving time, means just that: time that saves daylight.

A common misconception is that summer time adds an hour to the day. The length of daylight stays the same; only the numbers on the clock shift, pulling daily life earlier to match the sun.

The European Union turns its clocks back all at once at 1 a.m. Coordinated Universal Time on the last Sunday of October. In London, 2 a.m. becomes 1 a.m. again, so the 1 o'clock hour passes twice that night. That day effectively lasts 25 hours, while the spring day when clocks go forward lasts only 23.

Smartphones update on their own using network time, but oven and car clocks have to be changed by hand. If you have a trip to Europe or the US or an overseas video call around this time, remember that the time difference with Korea grows by an hour. During summer time the UK is 8 hours behind Korea, but once it ends, it is 9 hours behind.

Korea also used summer time several times starting in 1948, and the last time was 1987 to 1988, when Seoul hosted the Olympics. Since then it has not been brought back, because the benefits seemed small compared with the disruption to daily rhythms.

Many studies have found that the electricity actually saved was not large, and some point out that people are short on sleep for several days after losing an hour in spring. In 2019 the European Parliament voted to stop changing the clocks every year, but member states have not reached an agreement, so the practice continues. In the US, bills to fix the clock in one setting have also come up several times, but none has become law yet.