Daylight saving time happens twice a year in most of the United States

In the U.S., clocks move forward one hour on the second Sunday in March and back one hour on the first Sunday in November. When clocks spring forward in March, you lose an hour of sleep. When they fall back in November, you gain an hour. Not every state observes daylight saving time — Hawaii and most of Arizona do not change their clocks at all.

The exact dates shift each year because they are tied to specific Sundays rather than fixed calendar dates. In 2024, clocks moved forward on March 10 and back on November 3. In 2025, they will move forward on March 9 and back on November 2. You can find the dates for any year by checking the U.S. Department of Transportation website or your phone's calendar, which usually updates automatically.

Key Takeaways

  • Clocks move forward one hour on the second Sunday in March and back one hour on the first Sunday in November across most U.S. states.
  • Hawaii and most of Arizona do not observe daylight saving time and keep the same clock setting year-round.
  • The time change happens at 2 a.m. local time, so most people experience the shift when they wake up rather than during the day.
  • Your phone, computer, and most connected devices update automatically, but you may need to manually adjust clocks in older appliances, cars, and wall clocks.
  • The spring forward change can disrupt sleep and daily routines for a few days, while the fall back change is generally easier to adjust to.

What happens at the moment clocks change

The time change occurs at 2 a.m. local time. When clocks spring forward in March, 2 a.m. becomes 3 a.m. — that hour straightforward does not exist that night. When clocks fall back in November, 1 a.m. becomes 2 a.m. again — that hour repeats. Most people sleep through the change and notice it when they wake up.

Your smartphone, computer, and most modern appliances with built-in clocks update automatically if they are connected to the internet or a network. Older devices — wall clocks, car clocks, microwave displays, oven timers — do not update on their own and need to be adjusted by hand. Some people change these clocks the night before, while others wait until morning.

Which states and territories do not change their clocks

Hawaii and most of Arizona stay on the same time year-round and do not observe daylight saving time. A few U.S. territories also do not change — Puerto Rico, the U.S. Virgin Islands, Guam, American Samoa, and the Northern Mariana Islands keep steady time. Some counties in other states have chosen to stay on standard time permanently, though this is less common.

If you live in or travel to one of these places, you do not need to adjust your clocks. However, if you work or attend school across a state line where the other state does change its clocks, you may need to account for the one-hour difference during the transition weeks in March and November.

How the spring forward change affects sleep and routines

Losing an hour of sleep in March can throw off your sleep schedule for several days. Your body's internal clock — called your circadian rhythm — is used to waking and sleeping at certain times. When the clock jumps forward, your alarm goes off at what feels like an earlier time to your body, even though the clock says it is the normal time.

Most people adjust within a few days to a week. To ease the transition, some sleep experts suggest going to bed 15 to 20 minutes earlier for a few nights before the change, or spending extra time in bright light in the morning after the change to help reset your internal clock. The fall back change in November is usually easier because you gain an hour and can sleep longer.

Devices and systems that update automatically versus manually

Modern devices connected to the internet or a cellular network — phones, tablets, computers, smart home devices — update the time automatically. Your car's clock may update if it is connected to your phone via Bluetooth or if it has a built-in cellular connection, but many cars require manual adjustment. Check your car's manual or settings menu to see whether it updates on its own.

Devices that do not connect to a network need manual adjustment: wall clocks, kitchen timers, microwave displays, oven clocks, alarm clocks without internet, and older car clocks. Some people set reminders on their phones to adjust these clocks on the morning of the change. If you have many devices to adjust, doing it the night before can save time in the morning.

Planning around the time change at work and school

If your workplace or school uses an automated scheduling system, it usually handles the time change without your input. However, if you work shifts or have meetings scheduled near the time change, double-check the timing. A meeting listed as 9 a.m. on the day clocks spring forward might be scheduled for what your body perceives as 8 a.m., which can cause confusion.

If you work in healthcare, transportation, or another field where precise timing matters, your employer typically sends a reminder about the time change and how it affects your schedule. If you are unsure how the change affects your shift or schedule, ask your manager or check your employee handbook.

Why the United States observes daylight saving time

Daylight saving time was introduced during World War I to conserve fuel and was used again during World War II. It was brought back permanently in 1966 to align time zones across the country. The stated goal was to make better use of daylight hours and reduce energy consumption, though modern research shows the energy savings are small or nonexistent.

The practice remains controversial. Some states and territories have chosen not to observe it, and there have been repeated efforts in Congress to make daylight saving time permanent year-round or to eliminate it entirely. For now, the twice-yearly change remains the standard across most of the United States.

Frequently Asked Questions

Do I need to change the clocks in my home the night before or the morning of?

Either works. Many people change them the night before to avoid the rush in the morning, while others wait until they wake up. If you have a lot of manual clocks, doing it the evening before gives you more time. Your phone and computer will update automatically overnight if they are connected to the internet.

What time do clocks change exactly?

The change happens at 2 a.m. local time. In March, 2 a.m. becomes 3 a.m. In November, 2 a.m. becomes 1 a.m. Most people are asleep and do not notice the exact moment it happens.

Will my car clock update automatically?

It depends on your car's model and features. Newer cars with built-in cellular connections or Bluetooth links to your phone often update automatically. Older cars and some mid-range models require manual adjustment. Check your car's manual or settings menu, or ask your dealership if you are unsure.

How long does it take to adjust to the time change?

Most people adjust within three to seven days. The spring forward change is harder because you lose sleep, while the fall back change is usually easier. If you have trouble sleeping after the change, getting bright light exposure in the morning can help reset your internal clock faster.

What states do not change their clocks?

Hawaii and most of Arizona do not observe daylight saving time. Puerto Rico, the U.S. Virgin Islands, Guam, American Samoa, and the Northern Mariana Islands also stay on the same time year-round. A few counties in other states have opted out as well, though this is less common.