Daylight saving time: what changes, when, and what breaks
Clocks move an hour twice a year in some countries, on different dates, and the parts that break are never the clocks themselves.
The short answer
Clocks go forward an hour in spring and back an hour in autumn, in the countries that observe it — which is a minority of the world, mostly in North America, Europe, and parts of the southern hemisphere.
In 2026 the US changes on 2026-03-08 and 2026-11-01; the UK and EU on 2026-03-29 and 2026-10-25. The dates are not the same, and that mismatch is what breaks things.
What actually changes
Not the amount of daylight. The clock.
Going forward in spring shifts the whole civil day relative to the sun, moving an hour of daylight from the early morning — when most people are asleep — to the evening. Going back in autumn undoes it.
The offset from UTC changes with it. New York is UTC−5 in winter and UTC−4 in summer; London is UTC+0 and UTC+1.
The 2026 dates
| Region | Forward | Back |
|---|---|---|
| United States & Canada | 2026-03-08 | 2026-11-01 |
| UK & European Union | 2026-03-29 | 2026-10-25 |
| Australia (NSW, VIC, SA, TAS, ACT) | 2026-10-03 | 2026-04-04 |
Australia is in the southern hemisphere, so its seasons — and therefore its transitions — run opposite to the north.
The rules behind these dates: the US uses the second Sunday in March and the first Sunday in November. The EU uses the last Sunday in March and the last Sunday in October, and switches at the same UTC instant across the whole union rather than at a common local time.
Who does not observe it
Most of the world, by population. Nearly all of Asia including India, China and Japan. Nearly all of Africa. Most of South America. Within the US, Arizona (except the Navajo Nation) and Hawaii. Within Australia, Queensland, Western Australia and the Northern Territory.
Several countries have abandoned it in recent years. Anywhere near the equator has little reason to bother — day length barely varies.
What it actually breaks
Recurring meetings between regions that switch on different dates. Between 2026-03-08 and 2026-03-29 this year, the US has moved and Europe has not, so every transatlantic recurring call is an hour off for about three weeks. It happens again in reverse in autumn.
Any gap involving a non-observing country. India never changes, so its distance to New York moves by an hour twice a year without India doing anything. See IST to EST.
Abbreviations written by hand. "3pm EST" in July is not a real time, because the zone is on EDT then. See EST vs EDT.
The repeated and missing hour. In spring an hour does not exist; in autumn an hour happens twice. Both cause real problems for anything timestamped — logs, shift rotas, alarms. See what happens at 2am.
The defence
Schedule against cities, not offsets, and let the time zone database resolve the date. Use UTC for anything machine-read. And put a reminder in the calendar for mid-March and late October, which are the only two moments a standing cross-region arrangement can silently move.
Related: When does daylight saving time start? · Which countries still change their clocks?
Timezone: World Clock Widget
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Figures on this page are computed from the IANA time zone database. Last generated 2026-08-18.