Daylight saving time means setting clocks one hour ahead in the warm months and back in the cold ones. The sun keeps its schedule; only the clock's name for each moment changes. An hour of daylight moves from early morning to evening for part of the year, at the cost of darker mornings.
The clock moves, the sun does not#
Two names keep the seasons apart. Standard time is a region's normal offset from UTC, the reference time that ignores the seasons (UTC vs GMT: What Is the Difference and Which Should You Use?). Daylight saving time is standard time plus one hour: New York is UTC-5 in winter and UTC-4 in summer (EST vs EDT: What's the Difference, and Which One Is It Right Now?).
Take New York in 2026. Sunrise was about 6:21 a.m. on Saturday, March 7. The clocks then jumped from 2:00 to 3:00 a.m. on Sunday, and sunrise on Monday read about 7:18 a.m. That is 57 minutes later on the clock, even though the sun itself rose about three minutes earlier.
| New York, 2026 | What the clock does | Length of that day |
|---|---|---|
| Sunday, March 8 | 2:00 a.m. becomes 3:00 a.m.; 2:30 a.m. never happens | 23 hours |
| Sunday, November 1 | 2:00 a.m. becomes 1:00 a.m.; 1:30 a.m. happens twice, at 05:30 UTC and again at 06:30 UTC | 25 hours |
Computed from the IANA time zone database, release 2025b. Daylight saving adds no daylight: the sun is up for the same length of time on any date.
Why it was introduced, and when#
National governments waited for the First World War. timeanddate.com records a local change in Port Arthur, Ontario (now part of Thunder Bay) in 1908, and says Germany and Austria turned their clocks forward on April 30, 1916. Accounts give saving fuel and power as the reason, and other countries followed. The US adopted it in 1918 and standardized the dates in the Uniform Time Act of 1966, which lets a state exempt itself if the whole state does, according to a 2016 Congressional Research Service report. Today federal law runs it from the second Sunday in March to the first Sunday in November, according to the current CRS report.
Which countries use it, and which do not#
No official count exists, because the answer depends on what you count. timeanddate.com lists 70 countries using DST in 2026, fewer than 40% of the world's countries. Pew Research Center counted the 193 UN member states in 2023 and found about a third observe it, mostly in Europe. Our own check lands close: of the 244 countries and territories in Timelive's data, 70 have at least one place whose clock changes in 2026, going by the IANA time zone data. Some change only in part, such as the US, Canada, Australia and Mexico.
| Region | Clocks change in 2026 | Clocks stay fixed |
|---|---|---|
| Europe | All 27 EU members, UK, Norway, Switzerland, Ukraine | Iceland, Russia, Belarus, Turkey |
| North America | US, Canada, Cuba, Bahamas; Mexican border cities | Honolulu, Phoenix, Regina; most of Mexico |
| South America | Chile | Brazil, Argentina, Colombia, Peru, Uruguay |
| Africa | Egypt; Morocco is a special case (UTC+1 normally, UTC+0 for about five weeks around Ramadan, Feb 15 to Mar 22) | Nigeria, Kenya, South Africa |
| Asia and Middle East | Israel, Lebanon, Cyprus | India, China, Japan, South Korea, Indonesia, Saudi Arabia, UAE |
| Oceania | South-east Australia, New Zealand | Brisbane, Perth, Darwin |
The laws differ. Directive 2000/84/EC starts summer time in every EU member state at 1:00 a.m. Greenwich Mean Time on the last Sunday in March and ends it at the same moment on the last Sunday in October; the UK uses the same dates. In the US a state may opt out and stay on standard time all year, as Hawaii and most of Arizona do (US Time Zones Explained: Eastern, Central, Mountain, Pacific and Beyond). Rules also change: Brazil ended daylight saving in 2019, and Mexico in 2022 except near the US border.
The southern hemisphere runs the other way#
Seasons are reversed south of the equator, so daylight time covers the new year: it starts in spring (September or October) and ends in autumn (April). Chile follows the same pattern: in 2026 its clocks go back at 24:00 on Saturday, April 4 (to 23:00) and forward at 24:00 on Saturday, September 5 (to 01:00 on Sunday, September 6). The other 2026 changes, computed from the IANA data:
| Place | Clocks go back | Clocks go forward |
|---|---|---|
| Sydney | Sunday, April 5: 3:00 a.m. becomes 2:00 a.m. | Sunday, October 4: 2:00 a.m. becomes 3:00 a.m. |
| Auckland | Sunday, April 5: 3:00 a.m. becomes 2:00 a.m. | Sunday, September 27: 2:00 a.m. becomes 3:00 a.m. |
So on Friday, October 9, 2026, Sydney (UTC+11) is 15 hours ahead of New York (UTC-4), which has about three weeks of daylight time left. Not all of Australia follows: Queensland, Western Australia and the Northern Territory do not observe it, so Brisbane, Perth and Darwin keep one offset all year.
What it does to travel, meetings and software#
Regions change on different dates, so the gap between two cities wobbles. The US starts two to three weeks before the UK and EU and ends one week after them. In 2026 London is therefore four hours ahead of New York, not five, for 28 days in total (March 8 to 29, and October 25 to November 1). A weekly 3:00 p.m. London call is 10:00 a.m. in New York for most of the year but 11:00 a.m. in those weeks (How to Schedule a Meeting Across Time Zones: A 6-Step Checklist).
Software meets the same two awkward hours. A job set for 2:30 a.m. in New York has no such moment on March 8, 2026, and 1:30 a.m. happens twice on November 1, so the outcome depends on the program. Store the moment as UTC or a Unix timestamp (Unix Time, ISO 8601 and UTC: How Computers Store Time) and keep the zone name, such as America/New_York, not a fixed offset like -05:00. The rules live in the IANA time zone database, because governments set them and sometimes change them with little notice.
Does it save energy, and is it bad for your health?#
The original case was about fuel and light, but measured results are mixed. A US Department of Energy report on the 2007 US extension estimated electricity savings of about 0.5% per day during the extra weeks, roughly 0.03% of the year's use. A working paper on Indiana's 2006 move to statewide DST found about 1% more residential electricity use, which the authors attribute to extra heating and cooling outweighing the lighting saved. Neither study settles the question for every country.
Health research mostly studies the switch itself. The American Academy of Sleep Medicine says permanent standard time is the best choice for health and safety, arguing that seasonal switching pulls the body clock out of step with the social clock. One study of US fatal crashes from 1996 to 2017 estimated about a 6% higher risk in the week after the spring change (CU Boulder summary), though other researchers dispute how much of that comes from the clock change. These are observational findings, and a society's position is a policy judgment.
The permanent-time debate#
Ending the twice-a-year change means choosing one permanent clock, and the choice moves the daylight. New York in 2026 under each option, from the sunrise formula behind Timelive's city pages (almanac values can differ by a minute or two):
| New York, 2026 | Sunrise Dec 21 | Sunset Dec 21 | Sunrise Jun 21 | Sunset Jun 21 |
|---|---|---|---|---|
| Today's rule | 7:17 a.m. | 4:32 p.m. | 5:25 a.m. | 8:31 p.m. |
| Permanent standard time (UTC-5) | 7:17 a.m. | 4:32 p.m. | 4:25 a.m. | 7:31 p.m. |
| Permanent daylight time (UTC-4) | 8:17 a.m. | 5:32 p.m. | 5:25 a.m. | 8:31 p.m. |
Permanent standard time gives earlier summer mornings and evenings. Permanent daylight time gives later winter ones, with sunrise at about 8:17 a.m. on December 21. The US tried year-round daylight saving in 1974 and rolled it back that October, after complaints that included children going to school in the dark.
As of October 9, 2026, news reports say the House passed legislation making daylight saving time permanent in July; we did not confirm the House bill number or the vote count. We found no report of a Senate vote, so current law still applies; Congress.gov, where the Senate Sunshine Protection Act is S. 29, shows the latest status.
In the EU, the Commission proposed ending the changes in September 2018 and Parliament backed the idea in March 2019. The Council of the EU says it has not yet agreed its position, and we found no report that this has changed.
Frequently asked questions
How does daylight saving time work?
Clocks are set forward one hour on a fixed Sunday in spring and back one hour on a fixed Sunday in autumn. In between, local time is one hour later than standard time: New York, for example, moves from UTC-5 to UTC-4 and back.
The sun's timetable does not change, only the label on each moment. The two switch days last 23 and 25 hours.
Why do we have daylight saving time, and who invented it?
Mainly to save fuel and power in wartime: Germany and Austria changed their clocks nationwide on April 30, 1916, and other countries followed.
No single person invented it. Individuals proposed seasonal clock changes earlier, and Benjamin Franklin's 1784 essay, often named as the origin, was a satire that never suggested moving the clocks.
Which countries use daylight saving time?
About 70 in 2026, according to timeanddate.com, which is fewer than 40% of the world's countries; the exact figure depends on how partial and territorial use is counted. They include the US, Canada, the EU members, the UK, Chile, New Zealand and south-east Australia. India, China, Japan, Russia, Brazil and most of Africa keep one offset all year.
Does daylight saving time save energy?
Measured savings are small and inconsistent. A US Department of Energy report estimated that the 2007 US extension saved about 0.03% of a year's electricity, while a study of Indiana found residential use rose about 1%. Results depend on climate, habits and the dates used.
Is daylight saving time bad for your health?
The evidence concerns the twice-yearly switch more than the extra evening light. The American Academy of Sleep Medicine recommends permanent standard time, and one US study estimated about 6% more fatal crashes in the week after the spring change, though researchers dispute the size of that effect. This is general information, not medical advice.
Sources and further reading
- Daylight Saving Time Statistics — timeanddate.com
- Daylight Saving Time (DST) — Congressional Research Service, via EveryCRSReport
- Directive 2000/84/EC on summer-time arrangements — EUR-Lex, Publications Office of the European Union
- Impact of Extended Daylight Saving Time on National Energy Consumption — U.S. Department of Energy
- Does Daylight Saving Time Save Energy? Evidence from a Natural Experiment in Indiana — National Bureau of Economic Research
- Permanent standard time is the optimal choice for health and safety — American Academy of Sleep Medicine
- S.29, Sunshine Protection Act of 2025 — Congress.gov
- History of Daylight Saving Time (DST) — timeanddate.com
- Most countries don't observe daylight saving time — Pew Research Center
- Daylight Saving Time (CRS report R44411, 2016) — Congressional Research Service, via EveryCRSReport
- Spring forward to daylight saving time brings surge in deadly crashes — University of Colorado Boulder
- The U.S. tried permanent daylight saving time in the 1970s. Then quickly rejected it — NPR, via KUNC
- House Passes Legislation Making Daylight Saving Time Permanent — Bloomberg Government
- Time zone and daylight saving time data — IANA
- Seasonal time changes — Council of the European Union