Many people in the United States may have their circadian rhythm thrown off come Sunday morning, Nov. 2, due to daylight saving time ending.

Clocks will "fall back" to standard time this year at 2 a.m. local time on Sunday, Nov. 2, meaning those affected will gain an extra hour of sleep. The twice-a-year movement of clocks either backward or forward accounts for more daylight in the mornings or evenings for millions of Americans. With daylight saving time ending over the weekend, people affected can expect more daylight in the mornings.

While much of the country will be impacted by the time change, a few regions and states won't, including Hawaii, Arizona and some U.S. territories.

Here's what you need to know before daylight saving time ends overnight.

What is daylight saving time?

Daylight saving time, which occurs between March and November, is when most Americans adjust their clocks ahead by one hour.

Those affected by the time change gain an hour in November, as opposed to losing an hour in the spring, to make for more daylight in the winter mornings. When we "spring forward" in March, more daylight is visible in the evenings. And in the autumn, we "fall back."

Daylight saving time was first introduced in the United States in 1918 under the Standard Time Act as a measure to save on fuel costs during World War I by adding an extra hour of daylight, according to the Library of Congress.

After being abandoned at the federal level after WWI, the U.S. government reinstituted daylight saving time on an emergency basis throughout the mid to late 20th century. A uniform twice-a-year time change was then established through the Uniform Time Act of 1966.

Congress amended the Uniform Time Act in 2005, expanding daylight saving time to the period in effect today: Starting on the second Sunday of March and ending on the first Sunday of November, according to the Congressional Research Service. Yet again, this move was for energy-saving purposes.

When does daylight saving time end in 2025?

Daylight saving time comes to an end at 2 a.m. local time on Sunday, Nov. 2, 2025.

This year, daylight saving time comes a day earlier than last year and falls on the second-earliest possible date for the time change. Since daylight saving time falls on the first Saturday in November, the earliest possible date is Nov. 1.

In 2026, daylight saving time will begin again on Sunday, March 8.

Which locations in the US do not practice daylight saving time?

Hawaii and Arizona (excluding the Navajo Nation) do not observe daylight saving time and remain on standard time all year.

Neither do American Samoa, Guam, the Northern Mariana Islands, Puerto Rico or the U.S. Virgin Islands.

What is Trump's stance on daylight saving time?

President Donald Trump has previously shown support for ending daylight saving time permanently, calling it “inconvenient.”

"The Republican Party will use its best efforts to eliminate daylight saving time," Trump said on Truth Social in December 2024. "Daylight Saving Time is inconvenient, and very costly to our Nation."

Trump's tune changed a little earlier this year, as he noted that eliminating the time change would be a toss-up and would be difficult to rally support for.

"This should be the easiest one of all, but it's a 50-50 issue. If something's a 50-50 issue, it's hard to get excited. I assume people would like to have more light later, but some people want to have more light earlier, because they don't want to take their kids to school in the dark," Trump said in March, according to Reuters. "A lot of people like it one way, a lot of people like it the other way, it's very even."

In April, he said the House and Senate should push for more daylight at the end of the day, a stance consistent with his 2019 position, according to Politico.

Contributing: Fernando Cervantes Jr., Orlando Mayorquin, Bailey Allen & Kinsey Crowley/ USA TODAY

This article originally appeared on USA TODAY: Time for clocks to 'fall back'? Daylight saving time ends Sunday, Nov. 2.

Reporting by Jonathan Limehouse, USA TODAY / USA TODAY

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