What Is Daylight Saving Time?

How DST Works

During Daylight Saving Time, clocks are set forward by one hour from standard time. This shifts one hour of daylight from the morning to the evening. In the Northern Hemisphere, clocks typically advance in spring ("spring forward") and return to standard time in autumn ("fall back"). For the exact dates this happens, see the 2026 DST schedule or the 2027 DST schedule.

In the Southern Hemisphere, the seasons are reversed: DST begins in September or October and ends in March or April. Countries in the Southern Hemisphere that use DST include Australia, New Zealand, Chile, and Paraguay.

The transition usually happens at night to minimize disruption. In the United States, clocks change at 2:00 AM local time. In the EU, the change occurs simultaneously at 1:00 AM UTC. The effects of these transitions — both positive and negative — have been studied for decades.

Who Observes DST

Approximately 70 countries and territories observe DST in some form. The main regions that use it:

• North America — United States (most states), Canada (most provinces), parts of Mexico
• Europe — All EU member states, the UK, Switzerland, Norway, and others
• Oceania — Parts of Australia, New Zealand
• Middle East — Israel, Jordan, Lebanon, parts of Palestine
• South America — Chile, Paraguay

Most of Africa, Asia, and equatorial regions do not observe DST, since day length varies little near the equator. Some places that previously used DST have recently stopped, including Russia, Brazil, and most of Mexico.

See the full country-by-country DST table for 248 countries →

Why DST Was Introduced

Benjamin Franklin jokingly suggested the idea in 1784, proposing that Parisians could save candle wax by waking earlier. The modern concept was proposed independently by New Zealand entomologist George Hudson in 1895 and British builder William Willett in 1907.

Germany became the first country to adopt DST in 1916, during World War I, to conserve coal. Other countries followed. The United States adopted it in 1918, repealed it after the war, then reinstated it during World War II. The current US schedule has been in effect since the Energy Policy Act of 2005, which extended DST by four weeks starting in 2007.

Read the full history of DST →

Current Rules by Region

United States and Canada

DST runs from the second Sunday in March to the first Sunday in November. Clocks change at 2:00 AM local time. This schedule has been in effect since 2007. See the exact dates for US DST in 2026 and 2027.

European Union and United Kingdom

DST (called "summer time") runs from the last Sunday in March to the last Sunday in October. The change happens simultaneously across Europe at 1:00 AM UTC. The EU proposed abolishing seasonal clock changes in 2018, but member states have not reached a final agreement and the proposal has stalled. See European DST dates for 2026.

Australia

DST runs from the first Sunday in October to the first Sunday in April in participating states (ACT, NSW, South Australia, Tasmania, Victoria). Queensland, Northern Territory, and Western Australia do not observe DST. See Australian DST dates for 2026.

New Zealand

DST runs from the last Sunday in September to the first Sunday in April. See New Zealand DST dates for 2026.

Notable Exceptions

Even within countries that observe DST, certain regions opt out. The full DST exceptions page covers each case in detail.

The Ongoing Debate

DST remains contentious. Supporters say it extends usable evening daylight for recreation and commerce. Critics cite health effects from disrupted sleep, increased heart attack risk after the spring transition, and questionable energy savings. For a balanced overview of the evidence on both sides, see the pros and cons of DST.

In the US, the Sunshine Protection Act passed the Senate in 2022 proposing permanent DST, but did not pass the House. Various states have passed their own resolutions to adopt permanent DST, contingent on federal action.

The EU's 2018 proposal to let member states choose permanent standard or summer time has stalled, with no implementation date set. For more on this, see the FAQ entry on planned European changes.

Last reviewed: March 2026. Data sources: official government publications and worldwideclock.com.