Twice a year, billions of people adjust their clocks by one hour, disrupting sleep schedules and confusing international meetings. This guide explains how DST works, which countries participate, and how to navigate the scheduling complications it creates.

A Brief History of Daylight Saving Time

Germany first adopted DST in 1916 as a wartime energy measure. The US followed in 1918 and made it permanent federal policy with the Uniform Time Act of 1966, though states can opt out, as Arizona and Hawaii have done.

How Daylight Saving Time Works

In spring, clocks are set forward by one hour, moving an hour of daylight from the morning to the evening. In autumn, clocks are set back, returning to standard time. The mnemonic “spring forward, fall back” captures the pattern. When clocks spring forward, the clock jumps from 1:59 AM directly to 3:00 AM. When clocks fall back, 1:00 AM to 1:59 AM occurs twice.

When Clocks Change: Major Regions

United States and Canada

Clocks spring forward on the second Sunday of March at 2:00 AM local time and fall back on the first Sunday of November at 2:00 AM. Arizona, Hawaii, and most of Saskatchewan do not observe DST.

European Union

EU member states spring forward on the last Sunday of March at 1:00 AM UTC and fall back on the last Sunday of October at 1:00 AM UTC. All member states switch at the same absolute moment. The UK follows the same schedule.

Australia and New Zealand

Because Southern Hemisphere seasons are reversed, Australian states that observe DST spring forward on the first Sunday of October and fall back on the first Sunday of April. New Zealand springs forward on the last Sunday of September and falls back on the first Sunday of April. Queensland, Western Australia, and the Northern Territory do not observe DST.

Who Observes DST and Who Does Not

Roughly 70 countries observe some form of daylight saving time, but the practice is concentrated in higher latitudes where seasonal daylight variation is significant. Most of Europe and North America participate. However, the majority of Africa, Asia, and South America do not. China, Japan, India, and most of Southeast Asia have never adopted DST or have long since abandoned it. Countries near the equator have little reason to shift clocks because daylight hours remain relatively constant throughout the year.

Regional exceptions are common: Arizona and Hawaii in the US, Queensland and Western Australia, and Brazil, which abolished DST entirely in 2019.

The DST Gap Weeks Problem

One of the most frustrating consequences of DST for international scheduling is that different countries switch on different dates. The US springs forward in early March, but Europe does not follow until late March. During those two to three weeks, the time difference between New York and London narrows from five hours to four. Similarly, when the US falls back in early November but Europe has already fallen back in late October, there is a brief period where the gap widens unexpectedly.

The Southern Hemisphere compounds the problem further. When it is spring in North America, it is autumn in Australia. One hemisphere is springing forward while the other is falling back, causing time differences to shift by two hours rather than one. A team with members in New York, London, and Sydney may find that their usual meeting time shifts three times in a single spring season as each region transitions independently.

Moves to Abolish Daylight Saving Time

The EU proposed ending DST in 2019, but member states have not reached consensus and the legislation has stalled. In the US, the Sunshine Protection Act passed the Senate in 2022 but was not taken up by the House. Meanwhile, Russia (2014), Turkey (2016), and Morocco (2018) have already switched to permanent standard or summer time.