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Speculative theory
Daylight Saving TimeAtlas
Conventions & Standards · Timekeeping & calendars
The Standard Time Act established federal time standards in the United States and introduced daylight saving time during World War I. Common public claims about why daylight saving time was created or what it achieves are frequently disputed by historians and public-health researchers.
Open the caseDaylight Saving Time4
- Documented · Congress has held hearings examining whether the United States should retain clock changes, adopt permanent daylight saving time, or prefer permanent standard time.
- Documented · Daylight saving time has a long record of political contention, wartime adoption, repeal, and later reinstatement in the United States and elsewhere.
- Official · Under current United States practice, daylight saving time begins at 2 a.m. on the second Sunday in March in most jurisdictions that observe it.
- Contested · Common public claims about why daylight saving time was created or what it achieves are frequently disputed by historians and public-health researchers.
Germany1
- Documented · Germany was among the earliest national adopters of daylight saving time during World War I.
National Institute of Standards and Technology1
- Official · Official United States guidance on daylight saving time rules is published by federal timekeeping authorities including NIST and the U.S. Naval Observatory.
Standard Time Act1
- Documented · The Standard Time Act established federal time standards in the United States and introduced daylight saving time during World War I.
Uniform Time Act of 19661
- Documented · The Uniform Time Act of 1966 provided a national framework for uniform daylight saving time observance while allowing states to opt out.
Other1
- Documented · Historical newspaper and archival records document early twentieth-century public debate over daylight saving as an energy, commerce, and lifestyle measure.