The clocks are altered twice a year for daylight saving time. In 2025:

• In the UK and much of Europe, the clocks go forward by one hour at 1 AM on the last Sunday in March, specifically on March 30, 2025, marking the start of British Summer Time (BST).
• The clocks go back by one hour at 2 AM on the last Sunday in October, specifically on October 26, 2025, ending BST and returning to standard time (Greenwich Mean Time in the UK).

In the United States, daylight saving time starts earlier, on the second Sunday in March (March 9, 2025) when clocks spring forward, and ends on the first Sunday in November. The mnemonic to remember this is "spring forward, fall back," meaning clocks are set ahead one hour in spring and set back one hour in autumn. This tradition aims to make better use of daylight during warmer months and has been in place for over 100 years in many regions.