DST in the United States: An Overview
The United States has observed daylight saving time since 1918, making it one of the longest-running national DST programs in the world. The rules have changed multiple times, and today the U.S. operates under the Energy Policy Act of 2005, which extended DST by four weeks starting in 2007.
Current Schedule
- Start: Second Sunday of March at 2:00 AM — clocks spring forward to 3:00 AM
- End: First Sunday of November at 2:00 AM — clocks fall back to 1:00 AM
- Duration: Approximately 8 months of the year (DST is now the majority of the year)
States That Do Not Observe DST
Arizona is the most notable state that does not observe DST. Its hot desert climate means residents prefer cooler morning hours, and extra evening sunlight only extends the brutally hot part of the day. The Navajo Nation within Arizona does observe DST, creating a patchwork effect.
Hawaii also does not observe DST. Located close to the equator, Hawaii's daylight hours vary little throughout the year, making DST unnecessary.
U.S. territories including Puerto Rico, Guam, the U.S. Virgin Islands, American Samoa, and the Northern Mariana Islands do not observe DST.
Historical Timeline
- 1918: First national DST under the Standard Time Act (repealed 1919)
- 1942–1945: Year-round "War Time" DST during World War II
- 1966: Uniform Time Act standardizes DST nationally
- 1974–1975: Year-round DST during the oil crisis
- 1987: DST extended by three weeks
- 2007: DST extended by four more weeks under the Energy Policy Act of 2005
The Push for Permanent DST
In 2022, the U.S. Senate unanimously passed the Sunshine Protection Act, which would make DST permanent — eliminating the twice-yearly clock change. As of 2025, the bill has not been enacted into law, requiring House passage and presidential signature. Multiple states have passed their own legislation supporting permanent DST, but federal law must change first.
Time Zones Affected
The continental U.S. has four time zones: Eastern, Central, Mountain, and Pacific. All four observe DST (except Arizona in the Mountain zone). Alaska and Hawaii are in their own time zones; Alaska observes DST, Hawaii does not.