The 2024 time change happened on March 10 at 2 a.m.

In the United States, clocks moved forward one hour on the second Sunday of March. If you live in a state that observes daylight saving time, your clocks jumped from 1:59 a.m. to 3:00 a.m. on March 10, 2024. This is called "springing forward," and it means you lost an hour of sleep that night.

The fall time change will happen on November 3, 2024, when clocks move back one hour at 2 a.m. At that point, 2:00 a.m. becomes 1:00 a.m., and you gain an hour of sleep.

Not every state follows this schedule. Hawaii, most of Arizona, and several U.S. territories do not observe daylight saving time at all. If you live in one of those places, your clocks did not change on March 10.

Key Takeaways

  • Daylight saving time in the U.S. starts on the second Sunday of March, when clocks spring forward one hour at 2 a.m.
  • The fall time change happens on the first Sunday of November, when clocks fall back one hour at 2 a.m.
  • Hawaii, most of Arizona, and U.S. territories like Puerto Rico and Guam do not change their clocks.
  • The time change affects your phone, computer, and most connected devices automatically, but some older devices and appliances may need manual adjustment.

Why the time change happens at 2 a.m.

The time change occurs at 2 a.m. because it is the least disruptive hour. Most people are asleep, so fewer schedules and systems are running. Overnight workers and shift changes happen around this time anyway, so the disruption to transportation, hospitals, and other services is smaller than it would be during business hours.

The exact moment matters because computer systems, power grids, and financial markets all need to know the precise second the change happens. If the change happened at noon, millions of people would be in the middle of work, and coordinating the shift across all systems would be much harder.

Which devices change automatically and which don't

Your smartphone, computer, and most modern devices change the time automatically. Operating systems like iOS, Android, Windows, and macOS include the daylight saving time schedule built in. When the time arrives, these devices update themselves without you doing anything.

Devices that may not change automatically include older car clocks, microwave displays, oven clocks, and some alarm clocks. Smart home devices like thermostats and security systems usually update automatically if they are connected to the internet, but older models may not. Check the manual for any device you are unsure about, or look for a settings menu that mentions time zone or daylight saving.

If you have a device that did not update on its own, you can change it manually by going into the settings and adjusting the time forward or backward by one hour.

How to prepare for the time change

The night before the time change, you can go through your home and update any clocks that do not change automatically. This includes wall clocks, alarm clocks, car clocks, and appliance displays. It takes only a few minutes and prevents confusion the next morning.

If you have a smart home system, check the app or settings to make sure it is set to your correct time zone. Most systems update automatically, but some older ones may need manual confirmation.

On the morning after the time change, double-check the time on your phone and any important devices before you leave the house. This is especially important if you have an appointment or need to catch a flight.

Why some places don't observe daylight saving time

Hawaii stopped observing daylight saving time in 1967 because the state is close to the equator and does not experience the same seasonal changes in daylight that mainland states do. The sun rises and sets at roughly the same time year-round, so shifting clocks forward does not create the same benefit.

Most of Arizona also does not observe daylight saving time, except for the Navajo Nation, which does. The state decided that the extra daylight in the evening was not worth the disruption, especially in a hot climate where people prefer to be outdoors in the cooler morning hours.

U.S. territories including Puerto Rico, Guam, the U.S. Virgin Islands, and American Samoa do not observe daylight saving time either. Each territory made its own decision based on local needs and geography.

What to do if you're confused about the time in your area

The easiest way to find out whether your location observes daylight saving time is to check your phone's time zone settings. Your phone knows your location and will show you whether daylight saving time is currently in effect. You can also search online for your state or territory name plus "daylight saving time" to find official information.

If you are traveling across state lines, remember that some states change and some do not. For example, if you drive from California to Arizona in March, Arizona will be one hour behind California because California has moved forward and Arizona has not. Your phone will update automatically when you cross the border, but it is good to be aware of the difference if you are meeting someone or catching a flight.

Frequently Asked Questions

Do I need to change my phone's time manually?

No. Your phone updates automatically on the night of the time change. Make sure your phone's time zone setting is correct for your location, and the update will happen on its own. You do not need to do anything.

What time should I set my clocks back in the fall?

In the fall, clocks move back one hour at 2 a.m. on the first Sunday of November. If your clock shows 2:00 a.m., you change it to 1:00 a.m. This means you get an extra hour of sleep that night.

Will my car's clock change automatically?

Most newer cars with connected systems update automatically. Older cars with manual clocks do not. Check your car's manual or settings menu to see whether your model updates on its own. If it does not, you can change it manually using the clock controls on your dashboard.

What happens if I miss the time change and show up an hour early?

If you arrive an hour early because you forgot about the time change, you will simply have to wait. There is no penalty or problem — you just arrived before you needed to. This is why it is helpful to check the time on your phone before leaving for an important appointment on the day of a time change.

Do I need to change my alarm clock?

If your alarm clock is a smartphone or connected device, it updates automatically. If it is a traditional alarm clock, you will need to change it manually. Remember that if you change your alarm the night before, it will go off one hour earlier than usual the next morning because the time has moved forward.