Daylight saving time (DST) — called summer time in the UK and most of Europe — is the practice of setting clocks one hour forward in spring and one hour back in autumn. The key thing to understand: DST does not create extra daylight. The sun rises and sets at exactly the same astronomical moment regardless of what your clock says. What DST does is shift when that daylight falls relative to your daily schedule, moving an hour of morning light to the evening.

When do the clocks change?

The dates vary by region:

Region	Clocks forward (spring)	Clocks back (autumn)
European Union	Last Sunday of March	Last Sunday of October
United Kingdom	Last Sunday of March	Last Sunday of October
United States & Canada	Second Sunday of March	First Sunday of November
Australia (most states)	First Sunday of October	First Sunday of April
New Zealand	Last Sunday of September	First Sunday of April

Australia and New Zealand observe DST too — but because they are in the Southern Hemisphere, their seasons are flipped, so their clocks spring forward in October (their spring) and fall back in April (their autumn).

Which countries don't observe DST?

The majority of the world's countries do not observe daylight saving time. Most of Africa, most of Asia (including China, Japan, India, and most of Southeast Asia), and most of the Middle East keep a fixed time year-round. In South America, most countries stay on standard time, though a few — notably parts of Brazil historically — have observed it. Even within countries that observe DST, there are exceptions: Arizona in the USA stays on standard time year-round (except for the Navajo Nation), as do Hawaii and several US territories.

How does DST affect sunrise and sunset?

When clocks spring forward in late March in London, sunrise suddenly shifts from around 06:00 to around 07:00 — a noticeably later start to the day. Sunset, however, moves from around 18:45 to 19:45, giving an extra hour of usable evening light. For many people this trade-off feels worthwhile in spring and summer. In autumn, when clocks fall back, the reverse happens: darker mornings become lighter, but evenings arrive an hour earlier.

The effect is most pronounced at high latitudes where the rate of daylight change is fastest. Near the equator, where daylight barely varies across the year, DST has almost no practical impact — which helps explain why tropical countries largely don't bother with it.

A brief history

The idea is often attributed to Benjamin Franklin, who in 1784 wrote a satirical essay suggesting Parisians could save candles by waking earlier — but he was joking. The first country to actually implement DST was Germany in 1916, during World War I, as a measure to save coal. The UK and other Allied nations quickly followed. The US adopted it during both World Wars and then made it permanent in 1966 with the Uniform Time Act.

The original justification — saving energy — has been questioned by modern research. Studies have generally found the energy savings to be modest at best, and in some climates non-existent, because heating and cooling demands often offset any lighting savings.

The debate about abolishing DST

The twice-yearly clock change is unpopular in many countries. Critics point to disrupted sleep, a documented spike in traffic accidents and heart attacks in the days following the spring change, and the general inconvenience of updating clocks and schedules. In 2019 the European Parliament voted to end the practice across the EU, leaving member states to choose permanently between summer time or standard time. As of 2026, however, no final date for abolition has been set, and the bloc remains divided on which permanent time to adopt. In the US, the Sunshine Protection Act — which would make DST permanent — has passed the Senate but has not become law.

Use the tool on the homepage to see exact sunrise and sunset times for your location, on any date — so you can always see how much daylight is actually available, regardless of what the clocks say.