Daylight Saving Time: Everything You Need to Know
Learn the history of daylight saving time, when clocks change worldwide, and why many want to end the practice.
Use the DST Checker
Check daylight saving time changes
What Is Daylight Saving Time
Daylight Saving Time, often abbreviated DST, is the practice of advancing clocks by one hour during the warmer months of the year. The idea is to shift an hour of daylight from the morning, when many people are still sleeping, to the evening, when they are more likely to be awake and active. Clocks 'spring forward' by one hour in the spring and 'fall back' by one hour in the autumn. The original motivation behind DST was to reduce energy consumption by making better use of natural daylight during waking hours, potentially reducing the need for artificial lighting in the evening. Whether it actually achieves this goal in the modern era, when air conditioning and electronic devices dominate energy use, is a subject of active debate.
When DST Happens
The specific dates of DST transitions vary by country and sometimes by region within a country.
Who Does Not Observe DST
Not everyone participates in DST, and the list of non-observers might surprise you.
The Debate Over DST
A growing movement questions whether DST is worth the disruption it causes. Studies have linked the spring clock change to a temporary increase in heart attacks, car accidents, and workplace injuries in the days following the transition. Sleep researchers consistently recommend permanent standard time over permanent DST, because standard time better aligns our social clock with our biological clock. The EU voted in 2019 to abolish mandatory clock changes, but implementation has been repeatedly delayed. In the United States, the Sunshine Protection Act, which would make DST permanent year-round, has passed the Senate but has not yet cleared the House. The debate ultimately comes down to whether the benefits of longer evening daylight outweigh the health and safety costs of shifting the clock twice a year.