Daylight saving time: next clock change

How daylight saving time works

Daylight saving time (DST), called summer time in Europe, moves the clocks forward for the warmer months so that sunrise and sunset happen an hour later by the clock. Nothing changes in the sky; the community simply agrees to get up an hour earlier relative to the sun. In winter the clocks return to standard time.

Of the 312 zones in the tz database, 101 change their clocks under the current rules (13 of them in the southern hemisphere, where summer time runs from about October to April). The rest, which include most of Asia, Africa and South America, keep one offset all year. Near the equator, where day length barely changes, there is little to gain from it.

Spring forward: the missing hour

When summer time starts, an hour of local time is skipped. In the United States the clocks jump from 1:59:59 AM to 3:00:00 AM; in 2027 that happens on Sunday, March 14, so 2:30 AM does not exist in New York that day. A meeting, alarm or scheduled job set for 2:30 has to go somewhere. The iCalendar standard behind calendar invitations reads it with the offset from before the gap, which makes it 3:30 AM EDT (RFC 5545); other software may choose 3:00, and a badly written script might skip the job or run it twice. In the EU the jump is from 2:00 to 3:00 CET (1:00 UTC), on Sunday, March 28, 2027.

Fall back: the repeated hour

When summer time ends, an hour happens twice. In New York on Sunday, November 7, 2027, the clock reads 1:30 AM once in EDT (UTC−4) and again an hour later in EST (UTC−5). Logs and timestamps written in local time without an offset become ambiguous for that hour, which is why servers should log in UTC. In the EU the repeated hour is 2:00–3:00 on Sunday, October 31, 2027.

United States and Canada

Federal law, 15 U.S.C. §260a, sets daylight saving time from 2:00 a.m. on the second Sunday of March to 2:00 a.m. on the first Sunday of November. The dates have moved several times: the Uniform Time Act of 1966 used the last Sunday of April to the last Sunday of October, a 1986 amendment moved the start to the first Sunday of April, and the Energy Policy Act of 2005 set today’s dates from 2007. A state may exempt itself from daylight saving time (a state split between two zones may also exempt only the part in one of them); it may not choose other dates. Hawaii and most of Arizona (but not the Navajo Nation) do not observe it, and neither do American Samoa, Guam, Puerto Rico and the Virgin Islands (NIST). The Department of Transportation, not NIST, oversees time zones and DST.

The Sunshine Protection Act, which would make daylight saving time permanent, passed the House of Representatives on July 14, 2026 (308–117) and is in the Senate Commerce Committee. It is not law, so the changes continue.

Canada follows the same dates where it observes DST, but 2026 changed the map: British Columbia, Alberta, the Northwest Territories and Manitoba stopped changing their clocks and now stay on their summer offset all year, as Yukon has since 2020. Saskatchewan has kept Central Standard Time all year since the 1960s (Regina since 1960, Swift Current since 1972, according to tzdata).

European Union and United Kingdom

Directive 2000/84/EC makes summer time start at 1:00 a.m. GMT on the last Sunday in March and end at 1:00 a.m. GMT on the last Sunday in October, in every member state at the same instant. The UK kept the same dates after leaving the EU: the Summer Time Act 1972, as amended in 2002, sets British Summer Time from 1 a.m. GMT on the last Sunday of March to 1 a.m. GMT on the last Sunday of October.

In 2018 the European Commission proposed ending the seasonal changes (about 4.6 million people answered its consultation, 84% in favour). The Parliament supported the proposal in March 2019, but the Council has not adopted a position, so the proposal is stuck and the clocks still change twice a year.

Why the gap between cities changes

Because North America and Europe change on different Sundays, their difference shifts for a few weeks each year. In 2027, the US moves forward 14 days before the UK and the EU, so for that stretch New York is four hours behind London instead of five and five behind Paris instead of six. In autumn the EU and UK move back a week before the US. The southern hemisphere moves the other way: when Europe goes forward in March, Sydney goes back in April, and the gap between London and Sydney swings from 11 hours to 9.

Countries that dropped it

Many countries have tried and abandoned daylight saving time. Recent examples from tzdata: Mexico ended it for most of the country in 2022, keeping it only near the US border; Morocco, which from 2018 kept UTC+1 and set its clocks back an hour for Ramadan each year, moved to permanent UTC+0 on September 20, 2026; and Cuba decided not to fall back on November 1, 2026, staying on UTC−4 until November 2027. Japan used it from 1948 to 1951, China from 1986 to 1991, and India briefly during the Second World War. Each place page on this site shows the full history for its zone.

Unusual rules

• Lord Howe Island (Australia) moves its clocks by only 30 minutes.
• Antarctica’s Troll station moves by two hours, from UTC+0 to UTC+2.
• Ireland’s law treats summer time (IST) as its standard time, so tzdata models winter as “negative” daylight saving time. The clocks move exactly as in the UK.
• The Chatham Islands (New Zealand) use UTC+12:45 in winter and UTC+13:45 in summer.

History

William Willett proposed moving the clocks in Britain in 1907. Germany was the first country to adopt daylight saving time, in 1916, starting on April 30 at 11 p.m.; the UK followed a few weeks later (Royal Museums Greenwich; PTB). In the United States, the Emergency Daylight Saving Time Energy Conservation Act of 1973 kept the clocks on daylight time through the winter of 1974; tzdata records EDT in New York from January 6, 1974. The current US dates have applied since 2007.