In the UK, clocks go forward one hour at 1am on the last Sunday in March and back one hour at 2am on the last Sunday in October. In 2026 the dates are 29 March and 25 October; in 2027 they are 28 March and 31 October. Check the government’s clock-change dates for future years.

1. In 1907 William Willett published The Waste of Daylight, proposing that clocks be advanced in summer so people could make more use of daylight in the evening.

2. Willett died in 1915, before Britain adopted summer time in 1916.

3. Willett was the great-great-grandfather of Coldplay singer Chris Martin.

4. During the First World War, Germany adopted daylight saving in 1916 and Britain followed a few weeks later, starting on 21 May.

5. Most European countries change their clocks, but some do not. Iceland, Belarus, Russia and Turkey are among the countries that remain on the same time throughout the year.

6. From 1968 to 1971, the UK experimented with year-round British Standard Time, one hour ahead of Greenwich Mean Time.

7. During the Second World War, clocks stayed one hour ahead of Greenwich Mean Time through the winter. From 1941, British Double Summer Time put them two hours ahead in summer; it was briefly reinstated in 1947.

8. The Daylight Saving Bill introduced by Rebecca Harris MP in 2010 called for an assessment of advancing clocks and a possible trial. It did not become law.

9. Hawaii and most of Arizona do not observe daylight saving time; the Navajo Nation in Arizona does. Several US territories also stay on standard time year-round.

10. Longer light evenings are one argument for clock changes; darker mornings and disruption to routines are among the arguments against them. Evidence on the effects is still debated.

Read more from Royal Museums Greenwich, the House of Commons Library and the US National Institute of Standards and Technology.