Why does daylight saving time exist?

Only Arizona and Hawaii are exempt from changing the time twice a year to account for daylight saving time.

Updated September 5, 2024 by the USAFacts team

The ritual of changing the clocks twice a year to get more daylight has been in place for more than 50 years. But debates in state legislatures and Congress show that there’s some interest in stopping the process.

At least 45 states have considered or passed legislation to shift to permanent daylight saving time or permanent standard time. In 2022, the Senate passed the Sunshine Protection Act, which would move the US to permanent daylight saving time. But the bill has not received a vote in the House of Representatives.

When did daylight saving time begin in the US?

Daylight saving time was originally implemented during WWI to help conserve fuel and power in the US, but the daylight saving procedures most people are now familiar with were established in 1966 and most recently changed in 2005.

History of daylight saving time

Time zones in the US began in the late 1800s to help railroad companies coordinate along time and to reduce the likelihood of trains crashing due to differences in how time was kept. Before this, there were over 144 local time zones in North America.

The government didn’t alter time zones until 1918, with the passage of the Standard Time Act of 1918. At that time, the Interstate Commerce Commission, which regulated railroads at the time, was put in charge of time zones.

In 1918, the agency started the first instance of daylight saving time in the US to help conserve fuel and power during World War I. The idea was that shifting time to get more daylight hours would reduce the need for lighting. After the war’s conclusion, daylight saving time was abolished nationally, with some states continuing the practice.

The founding of the Department of Transportation led to the current version of daylight saving time with the passage of the Uniform Time Act of 1966.

Daylight saving time now

The current dates for when the US springs forward (the second Sunday of March) into daylight saving time or falls back (the first Sunday of November) to standard time are enshrined in federal law and were most recently changed in the Energy Policy Act of 2005.

When does daylight saving time start and end?

In 2024, daylight saving time started on Sunday, March 10 will end on Sunday, November 3. It will begin again on Sunday, March 9, 2025 and run through Sunday, November 2.

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Which states have daylight saving time?

As of 2022, only Arizona and Hawaii have exempted themselves from the time change.

States are allowed to exempt themselves from daylight saving time but cannot set their schedules to it permanently.

Seventeen states have passed laws to observe permanent daylight saving time, while Kentucky and Ohio have passed resolutions supporting it. If Congress were to change federal law regarding daylight saving time, these laws and resolutions could come into effect.

Sunshine protection act

The US Senate unanimously passed the Sunshine Protection Act in 2022, which would move the nation to permanent daylight saving time. The bill has not received a vote in the House of Representatives.

Are there benefits to daylight saving time?

There have been several studies on how seasonal daylight saving time impacts people.

In 1974, a Transportation Department daylight saving time study found no conclusive difference in energy usage, crime, travel times, or trade during the time shift. A separate report on whether the practice increased traffic fatalities involving school children was inconclusive.

In 2008, an Energy Department study showed energy consumption dropped 0.02% due to daylight saving time. The study also showed no “measurable impact” on vehicle gas consumption.

An academic study cited in a Congressional Research Service report found evidence of some increase in heart attacks during transitions to or out of daylight saving time.

What parts of the US get the most daylight during working hours?

One goal of daylight saving time is to have more days with sunlight during working hours.

The amount of daylight an area gets differs based on its location. Northern cities tend to get more dark days, or days with less than 10 hours of daylight in a year. A city’s location within a time zone matters, too. The further west a city is in a time zone, the later its sunrises and sunsets will be.

Shifting to permanent daylight saving time would affect some cities more than others. Bangor, Maine would have 98 more sunrises after 7 a.m. if it were on permanent daylight saving time. But Washington, DC, which is further west than Bangor, would get 44 more sunrises after 7 a.m.

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