Each spring and autumn millions adjust their clocks for daylight saving time (DST) — a twice-yearly ritual aimed at shifting daylight into evening hours. DST is mainly used in temperate regions, where the gap between long summer days and short winter days makes a clock change seem useful. Newcomers often rely on the old mnemonic: “spring forward, fall back” — clocks move an hour ahead in spring and an hour back in autumn. In the Northern Hemisphere the changes typically fall in March and October; in the Southern Hemisphere (for example Australia, New Zealand and Chile) the pattern is reversed.
Only about a third of the world’s countries observe DST. Much of Africa, most of Asia and tropical nations skip it entirely. Even inside countries that use DST, participation can be uneven. In the United States, Hawaii and most of Arizona do not observe DST; the Navajo Nation in northeastern Arizona does, while the Hopi Reservation it surrounds does not, creating a local “donut” where travelers can pass multiple time changes in a short drive. Not all Australian states adopt DST, though New Zealand applies it nationwide.
The modern idea of moving clocks for extra evening daylight began with a New Zealander. In 1895 postal worker and amateur entomologist George Vernon Hudson proposed shifting clocks to free up evening hours for insect collecting and leisure activities such as gardening and sport. A decade later British builder William Willett independently promoted the same concept after noticing wasted morning daylight during a 1905 ride; his pamphlet The Waste of Daylight attracted supporters including Winston Churchill and Arthur Conan Doyle, but Parliament repeatedly rejected it and Willett campaigned until his death in 1915. Wartime pressures changed attitudes: Germany was the first country to adopt DST officially during World War I to conserve coal, and Britain, France and the United States followed within a year.
DST has gathered myths and misunderstandings. A frequent misattribution credits Benjamin Franklin with inventing DST; his 1784 essay jokingly suggested rising earlier to save candles but did not propose changing clocks. Another persistent misconception is that DST helps farmers; many in agriculture oppose it because livestock and farming schedules do not shift with human clock changes.
A quirk of modern lore links DST to Halloween. Michael Downing’s 2009 book Spring Forward asserted that candy-industry interests lobbied to extend DST past October to stretch trick-or-treating and boost sales; industry representatives deny an organized campaign. Congress did extend DST in the Energy Policy Act of 2005, moving the end to the first Sunday in November starting in 2007 — a change that invited speculation about motives.
Research shows clock changes can affect behavior and safety. A 2012 Journal of Applied Psychology study found a rise in workplace “cyberloafing” on the Monday after clocks spring forward, as sleep-deprived employees struggled to concentrate. A 2020 Current Biology paper reported a roughly 6% increase in fatal car crashes in the United States during the week after the spring shift.
The politics of DST remain unsettled. In the U.S. the Sunshine Protection Act to make DST permanent passed the Senate in 2022 but stalled in the House. In April 2025 former president Donald Trump urged Congress on Truth Social to push for “more Daylight at the end of a day,” calling the clock changes costly. Public opinion appears to be shifting: a YouGov poll in February 2026 found 64% of Americans would prefer ending the twice-yearly clock changes, with many favoring permanent DST (later sunrises and sunsets). The European Union has debated scrapping the practice for years, but no universal change has been adopted.
For now, millions will grumble about losing an hour’s sleep when clocks jump forward on March 29 — and look forward to reclaiming it when clocks fall back on October 25.
Edited by Elizabeth Grenier.