ATLANTA — When do clocks fall back? As daylight saving time 2025 ends, we gain an extra hour of sleep.
Next weekend, it will be time to change any of your clocks that don’t automatically adjust.
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Just a couple of days after Halloween, most of the US will be moving the clocks backward one hour. Daylight Saving Time (DST) ends on Nov. 2, with the time officially changing at 2 a.m.
Why do we use this system of “spring forward” and “fall back” when it comes to our clocks?
Here’s a look at the history of DST:
How did it get started?
We can blame New Zealand entomologist George Hudson for daylight saving time. He wanted extra hours after work to go bug hunting, according to National Geographic, so he came up with the idea of just moving the hands on the clock.
William Willett, who is the great-great-grandfather of the band Coldplay’s Chris Martin, arrived at the same idea a few years later and proposed moving the clock forward in the spring and back in the fall in his work, “British Summer Time.”
Willett’s idea was picked up a few years later by the Germans, who used it during World War I as a way to save on coal use. Other countries would soon follow suit, most with the idea that it would be a cost-saving measure.
President Woodrow Wilson agreed that DST was a good idea and, in 1918, he signed legislation that would shift the country to the new time system.
Who uses DST?
While most of the country and about 40% of the world use DST, there are some exceptions. Arizona, Hawaii and several U.S. territories don’t fall back or spring forward with DST.
Arizona has not observed DST since 1967, when they filed for an exemption under the DST exemption statute. Hawaii, too, opted out under that exemption. The state has never used DST.
The Uniform Time Act of 1966 mandates the country use daylight saving time but allows states to exempt themselves from the practice and stay on standard time — the local time in a region when DST is not in use.
While states can stay on standard time, they cannot permanently stay on DST.
Confused? You’re in good company. Full-time DST would require an act of Congress to make a change.
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Here’s what to know about the twice-yearly ritual.
How the body reacts to light
The brain has a master clock that is set by exposure to sunlight and darkness. This circadian rhythm is a roughly 24-hour cycle that determines when we become sleepy and when we’re more alert. The patterns change with age, one reason that early-to-rise youngsters evolve into hard-to-wake teens.
Morning light resets the rhythm. By evening, levels of a hormone called melatonin begin to surge, triggering drowsiness. Too much light in the evening — that extra hour from daylight saving time — delays that surge and the cycle gets out of sync.
And that circadian clock affects more than sleep, also influencing things like heart rate, blood pressure, stress hormones and metabolism.
How do time changes affect sleep?
Even an hour change on the clock can throw off sleep schedules — because even though the clocks change, work and school start times stay the same.
That’s a problem because so many people are already sleep deprived. About 1 in 3 U.S. adults sleep less than the recommended seven-plus hours nightly, and more than half of U.S. teens don’t get the recommended eight-plus hours on weeknights.
Sleep deprivation is linked to heart disease, cognitive decline, obesity and numerous other problems.
How to prepare for the time change
Some people try to prepare for a time change jolt by changing their bed times little by little in the days before the change. There are ways to ease the adjustment, including getting more sunshine to help reset your circadian rhythm for healthful sleep.
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Will the U.S. ever get rid of the time change?
Lawmakers occasionally propose getting rid of the time change altogether. The most prominent recent attempt, a now-stalled bipartisan bill named the Sunshine Protection Act, proposes making daylight saving time permanent. Health experts say the lawmakers have it backward — standard time should be made permanent.
Nineteen states, including Georgia, have enacted legislation to provide for year-round daylight saving time if Congress were to enact a bill allowing such a change.
The U.S. territories of the American Samoa, Guam, the Northern Mariana Islands, Puerto Rico and the Virgin Islands observe permanent standard time.
The Associated Press contributed to this article.
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