Twice a year, much of the United States, Canada and Europe moves the clocks. The idea is often credited to Benjamin Franklin, but his 1784 essay about Parisians getting up earlier to save candles was a satirical letter, not a proposal to change clocks. The real history is more practical and more recent.
Key Takeaways
- Germany adopted daylight saving time in 1916 during World War I to save fuel; many countries followed.
- The US Uniform Time Act of 1966 standardised daylight saving time, though states may opt out.
- Since 2007, US daylight saving time runs from the second Sunday in March to the first Sunday in November.
- Proposals to make daylight saving time permanent have been introduced in Congress but have not become law.
Early ideas
New Zealand entomologist George Hudson proposed shifting clocks in 1895 so he would have more daylight after work to collect insects. In Britain, builder William Willett campaigned in the early 1900s for moving clocks in summer.
The wartime start
Germany and Austria-Hungary introduced daylight saving time in 1916 to conserve coal. Britain and other countries quickly followed. The US adopted it in 1918, though it was repealed nationally after the war, with some local areas keeping it.
During World War II the US adopted year-round “War Time” from 1942 to 1945.
The 1966 Uniform Time Act
After the war, local rules varied widely, causing confusion for transport and broadcasting. The Uniform Time Act of 1966 set national start and end dates while allowing states to stay on standard time all year. Hawaii and most of Arizona do not observe daylight saving time, and neither do several US territories.
The 1974 experiment
During the 1973 oil crisis, Congress put the country on year-round daylight saving time starting January 1974. Dark winter mornings proved unpopular, and the law was changed in late 1974 to return to standard time in winter.
Current US dates
The Energy Policy Act of 2005 extended daylight saving time from 2007. It now starts at 2 a.m. on the second Sunday in March and ends at 2 a.m. on the first Sunday in November.
Does it save energy?
Studies have reached different conclusions. A US Department of Energy study of the 2007 extension found a small reduction in electricity use. Other research has found little effect or even increases from greater heating and cooling use.
The health debate
Sleep scientists have raised concerns about the spring transition, which shortens sleep and has been linked in research to short-term increases in heart attacks and traffic accidents. The American Academy of Sleep Medicine supports permanent standard time, arguing it better matches the body’s natural rhythms.
Permanent daylight time?
The Sunshine Protection Act, which would make daylight saving time permanent, passed the US Senate by unanimous consent in 2022 but did not pass the House. It has been reintroduced since. Many states have passed laws to adopt permanent daylight saving time if Congress allows it. Federal law currently allows states to stay on permanent standard time, but not permanent daylight time.
Frequently Asked Questions
Is it “daylight saving” or “daylight savings”? The official term is daylight saving time, although “savings” is common in speech.
Does the whole world change clocks? No. Most countries near the equator and many others do not use daylight saving time.
Why 2 a.m.? It was chosen to minimise disruption, when few trains were running and most people were asleep.
The bottom line
Daylight saving time began as a wartime fuel measure and became a twice-yearly habit. Whether to keep switching, or which time to keep, is still a live debate.
