What to Know About Daylight Saving Time as Another Clock Change Looms

It’s almost that time of year again.

Starting in just a few days, the sun will appear to rise later in the morning and set later in the evening in most of the U.S. thanks to the long-standing—and controversial—practice known as Daylight Saving Time.

The practice of changing the clocks twice a year is unpopular, dubiously effective in achieving its intended aims, and criticized by many experts for its health effects. While the majority of the U.S. continues to jump forward and back an hour each year, some American lawmakers have proposed making Daylight Saving Time permanent. Most other countries don’t observe the practice, including several that have opted to end it within the past decade.

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Read more: The Dark Side of Daylight Saving Time

Here’s everything you need to know about Daylight Saving Time this year.

When do the clocks go forward in March 2026?

For the states that observe it, Daylight Saving Time begins on the second Sunday in March each year. In 2026, that is March 8, meaning that at 2 a.m. local time on Sunday, the clocks will move forward by one hour, to 3 a.m.

How does Daylight Saving Time work?

Under Daylight Saving Time, the clocks jump forward by an hour every March, effectively shifting the hours in which daylight appears.

That shift in the clocks lasts for more than half a year, until Daylight Saving Time ends in November. After that point, the sun appears to rise earlier in the morning and set earlier in the evening again—until the following March, when Daylight Saving Time starts once more.

Why do we have Daylight Saving Time?

Daylight Saving Time is meant to better align daylight hours with the times people are most active during the part of the year when the weather is typically warmer.

Initially, the practice was established in the U.S. as part of an energy conservation effort during World War I, though there are conflicting reports on whether observing Daylight Saving Time actually helps conserve energy.

How does Daylight Saving Time affect your health?

Many experts have criticized Daylight Saving Time, saying that the practice impacts sleep and overall health. Experts previously told TIME that changing the clocks twice a year disrupts people’s sleep and circadian rhythm, which is associated with broader negative impacts on their health. Some studies, for instance, have found a link between Daylight Saving Time and a greater risk of stroke. It has also been associated with a greater risk of motor vehicle accidents.

“The spring time change leads to society-wide sleep deprivation,” Jennifer Martin, former president of the American Academy of Sleep Medicine, previously told TIME.

Which states don’t participate in Daylight Saving Time?

The majority of U.S. states participate in Daylight Saving Time. The two exceptions to that are Hawaii and most of Arizona, which remain on Standard Time year-round. The Navajo Nation, within Arizona, does observe Daylight Saving Time, however.

The U.S. territories of American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the U.S. Virgin Islands also don’t observe Daylight Saving Time.

The post What to Know About Daylight Saving Time as Another Clock Change Looms appeared first on TIME.