Daylight saving time

A map showing countries that use daylight saving according to each hemisphere as of April 2023. DST in the northern hemisphere summer DST in the southern hemisphere summer DST no longer used DST never used

Clocks are advanced by one hour during the very early morning at the beginning of DST.

When DST ends, clocks are set back (as if to repeat one hour) during the very early morning. Specific times vary.

Daylight saving time (DST) or summer time (ST) is a time to keep during summer. During the summer months, the sun stays visible for a longer time, and sunset happens late in the day. For this reason, certain countries advance the time by one hour near the start of summer, and put it back one hour during autumn.

DST helps stores that sell to people after they get off work, and it doesn't hurt farmers and others whose hours are set by the sun. It cuts traffic accident rates. Sometimes it can reduce energy costs, but it can also increase them.

Most of the world's countries do not use DST, but it is common in Europe and North America.

The United States, Australia, the United Kingdom, Canada and many other countries have DST. These countries also have regions that do not have DST:

United States: most of Arizona and Hawaii
Australia: Queensland, Western Australia and the Northern Territory
Canada: Saskatchewan except for a few locations with the border with Alberta and Manitoba, and the Yukon Territory

Iceland, Russia, Belarus, and some parts of Ukraine are countries in Europe without DST.

Europe

Since 1971 all clocks in the European Union have changed on same dates and at the same time, 06:00 GMT.^[1]

European Summer Time begins (clocks go forward) at 01:00 UTC on the last Sunday in March, and ends (clocks go back) at 01:00 UTC on the last Sunday in October:

Start	End
28 March 2021	31 October 2021
27 March 2022	30 October 2022
26 March 2023	29 October 2023
31 March 2024	27 October 2024
30 March 2025	26 October 2025^{[note 1]}
29 March 2026 ?	25 October 2026
28 March 2027 ?	31 October 2027

↑ If the 2018 Commission proposal had been approved by the Council of Ministers, and member states opted to remain on winter time year round, the October 2022 clock change would have been the final clock change.

United States

The following table lists future starting and ending dates of daylight saving time in the United States:

Year	Start	End
2021	March 14	November 7
2022	March 13	November 6
2023	March 12	November 5
2024	March 10	November 3
2025	March 9	November 2
2026	March 8	November 1
2027	March 14	November 7

Permanent GMT+1

Permanent Summer Time has support in some northerly countries such as the UK. It was tried in the British Standard Time experiment, with Britain remaining on GMT+1 throughout the year. This took place between 27 October 1968 and 31 October 1971.

There are proposals for GMT+1 in the winter, and DST summer time (GMT+2) in the summer. In favour are most city dwellers: children do not have to come home after school in the dark, and late afternoon and early evening activities benefit. In favour also were those concerned with accidents, because both accidents and fuel consumption go down.RoSPA suggests this would reduce the number of accidents over this period as a result of the lighter evenings.^[2]^[3]^[4]

Against are many farmers in northerly latitudes, because sunrise would occur in winter at about 10:00 in the morning. However, in March 2010 the National Farmers Union said that it was not against Single/Double Summer Time, and is in fact relatively neutral, with many farmers expressing a preference for the change.^[5]

Automatic adjustment

Most mobile phones and computers connected to the Internet will automatically adjust their clocks for DST. Some computers will not adjust or will adjust the time incorrectly or on the wrong date. Also, computers with more than one operating system may be incorrectly adjusted twice or more when each operating system boots.

Daylight Saving Time Media

An ancient water clock that lets hour lengths vary with season.
George Hudson was the first to propose modern DST, in 1895
DST was first implemented in the United States to conserve energy during World War I. (poster by United Cigar Stores)
Retailers generally favor DST; United Cigar Stores hailed a 1918 DST bill.
William Willett independently proposed DST in 1907 and advocated it tirelessly.^[6]
A 2001 US public service advertisement reminded people to adjust clocks.
The William Willett Memorial Sundial in Petts Wood, south London, is always on DST.