As the saying goes, "spring forward, fall back." But why does the time change at 2 a.m.?
Why Does Daylight Saving Time Start at 2 a.m.?
Updated on Feb. 12, 2025
We’ve all experienced the shift to and from daylight saving time—whether we like it or not. In decades past, we’d wake up to clocks running an hour behind or ahead, and we’d adjust them by hand to fit the new time. These days, the clocks we use most often (like those on our phones and computers) tend to automatically jump forward an hour in spring and fall back an hour in autumn. You probably barely give the shift a thought beyond how it’ll affect your sleep. But have you ever stopped to wonder: Why does the time change at 2 a.m.? And how were the specific dates chosen?
Below, we’re diving deep into the history of daylight saving time (or DST), the reasoning behind its precise timing and what to expect when the clocks change in 2025.
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What is daylight saving time?
On the second Sunday of March each year, shortly before the spring equinox, clocks are set forward one hour at 2 a.m. This kicks off daylight saving time, which aims to give people an opportunity to make better use of daylight while they are awake. By contrast, clocks go back an hour on the first Sunday of November every year. These rules have led to the popular and easy-to-remember saying “spring forward, fall back.”
Daylight saving time—also known as daylight time or summer time in the U.K. and other regions of Europe—was once proposed to the city of Paris in a satirical essay by Benjamin Franklin (yes, that Benjamin Franklin!). Despite the DST concept resurfacing throughout the years, it didn’t become law in the United States until 1918.
While we’re on the topic, an important note: It’s daylight saving time, not—as is commonly but mistakenly said—daylight savings time.
Why does daylight saving time start at 2 a.m.?
Instead of adjusting the clocks at midnight, as might be expected, we officially change the time at 2 a.m. because of railroad schedules. When DST was introduced during World War I, it was one of the few times when there were no trains traveling on the tracks. “Sunday morning at 2 a.m. was when they would interrupt the least amount of train travel around the country,” Michael Downing, author of Spring Forward: The Annual Madness of Daylight Saving Time, explained to Time.
According to the online museum WebExhibits, the 2 a.m. change was also a convenient middle ground between midnight—when changing the clocks would require the date switching back to the previous day—and later in the morning, when early shift workers and churchgoers might be affected.
Why does daylight saving time start in March?
Daylight saving is all about conserving natural light during the spring, summer and early fall days, making March the ideal month to put the DST practice into effect. Those needs lessen as fall kicks into high gear, which is why DST ends in November.
What, exactly, happens when daylight saving time begins and ends?
When the time changes at 2 a.m. in March, the clocks jump ahead an hour. Meanwhile, when daylight saving time ends in November, about six weeks after the fall equinox, the clocks go back an hour.
Luckily, your smartphones, tablets and computers typically adjust the time and date automatically, so you don’t have to worry about being late—or early—for church, yoga, brunch or any other Sunday-morning plans. But don’t forget to manually change your other clocks (including those on your oven and microwave)!
When does daylight saving time spring forward and fall back in 2025?
In 2025, daylight saving time starts on Sunday, March 9, and ends on Sunday, Nov. 2. Here are the dates for the next three years:
- 2026: Sunday, March 8, to Sunday, Nov. 1
- 2027: Sunday, March 14, to Sunday, Nov. 7
- 2028: Sunday, March 12, to Sunday, Nov. 5
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Sources:
- Time: “Why Does Daylight Saving Time Start at 2 a.m.?”
- WebExhibits: “When We Change Our Clocks”
