Daylight saving time changes happen twice a year in most of the US

In 2024 and beyond, clocks spring forward on the second Sunday in March and fall back on the first Sunday in November. In March, you lose an hour of sleep; in November, you gain one back. The change happens at 2 a.m. local time, though most people adjust their clocks before bed the night before.

Not every state observes daylight saving time. Hawaii and most of Arizona stay on standard time year-round. Some US territories like Puerto Rico, Guam, and the US Virgin Islands also do not change. If you live in one of these places or are traveling to one, your devices may change automatically but the local time will not.

The exact dates are set by federal law (the Uniform Time Act of 1966), so they are the same across every state that does observe the change. This means if you work across state lines or communicate with people in different zones, the transition happens on the same calendar day everywhere.

Key Takeaways

  • Clocks spring forward one hour on the second Sunday in March and fall back one hour on the first Sunday in November.
  • The change occurs at 2 a.m., though most people adjust clocks the evening before.
  • Hawaii, Arizona (except the Navajo Nation), and US territories do not change their clocks.
  • Your phone and computer usually update automatically, but older appliances and car clocks may need manual adjustment.
  • The time change can affect sleep, medication schedules, and any appointment or meeting set for the early morning hours.

Which devices update automatically and which do not

Smartphones, tablets, and computers connected to the internet update automatically when daylight saving time begins and ends. Your device checks the network time and adjusts without you doing anything. This is true for iPhones, Android phones, Windows computers, and Macs.

Appliances and older devices often do not update on their own. Microwave clocks, oven displays, car clocks, wall clocks, and alarm clocks that are not connected to the internet will show the wrong time until you change them manually. Some newer car models update automatically if they have a connected infotainment system, but many do not.

Smart home devices like Alexa speakers and Google Home devices update automatically if they are connected to Wi-Fi. Thermostats vary: some smart thermostats update themselves, while older programmable thermostats may need you to adjust them by hand or reprogram their schedule.

How the time change affects your sleep and routine

Losing an hour in March is harder on most people than gaining an hour in November. When clocks spring forward, you go to bed at your normal time but wake up an hour earlier by the clock. Your body does not actually sleep less, but the sudden shift can leave you feeling groggy for a few days.

The disruption is real enough that hospitals and safety researchers track it. Car accidents and workplace injuries tend to increase slightly in the days after the spring change. If you have a strict medication schedule, a medical appointment, or a time-sensitive commitment on the day of the change, write it down with both the old time and the new time so you do not miss it.

Children and older adults often feel the change more noticeably. If you have young kids, you may want to shift bedtime gradually in the days before the change rather than all at once. For people with sleep disorders or those taking medications tied to specific times, talking to a doctor before the change can help you plan the adjustment.

What happens to your work schedule and meetings

If your job involves scheduled calls, shifts, or meetings with people in different time zones, the change can create confusion. A 9 a.m. meeting in New York will be a different time in Arizona (which does not change) or in Hawaii. Calendar software usually handles this automatically if your time zone is set correctly, but it is worth double-checking important meetings the day before.

If you work night shifts, the spring change means your shift is one hour shorter that night (you clock out at the same wall time but fewer hours have passed). In November, your night shift is one hour longer. Some employers adjust pay for this; others do not. Check your employee handbook or ask your manager if you are unsure how your pay is calculated on the change dates.

Remote workers and freelancers should update their calendar time zone settings before the change date. If a client or colleague is in a state that does not observe daylight saving time, make sure you both know what time you are meeting in each zone.

Preparing your home and appliances for the change

A week before the change, make a list of devices that need manual adjustment: car clock, microwave, oven, bedroom alarm clock, wall clocks, and any other appliance with a built-in clock. Some people change them all on the evening before; others do it gradually over a few days.

If you have a programmable thermostat, check whether it updates automatically or needs to be adjusted by hand. The same goes for any smart home devices that are not connected to Wi-Fi. Older security systems and time-locked safes may also need adjustment.

For your car, check your owner's manual to see whether the clock updates automatically. Many newer vehicles do, but if yours does not, you can usually adjust it from the dashboard menu. Some cars require you to use the steering wheel buttons or a touchscreen; others have a dedicated clock button.

Time zones and daylight saving time across the US

The continental US spans four time zones: Eastern, Central, Mountain, and Pacific. When daylight saving time changes, all four zones change on the same day and at the same moment (2 a.m. in each zone). This means the time difference between zones stays the same before and after the change.

Alaska and Hawaii are on their own time zones and do not observe daylight saving time, so they stay on standard time year-round. This means Alaska is one hour behind the Pacific zone during daylight saving time but two hours behind during standard time. Hawaii is three hours behind Pacific during daylight saving time and two hours behind during standard time.

If you are traveling across the country around the change date, pay attention to your destination's time zone and whether it observes daylight saving time. A flight landing in Arizona at 3 p.m. Pacific time will arrive at 4 p.m. Arizona time (since Arizona does not change), even though the time zones are normally one hour apart.

Why the US has daylight saving time

Daylight saving time was introduced during World War I to conserve fuel and was used again during World War II. It became permanent in most of the US in 1966 under the Uniform Time Act. The stated goal was to make better use of daylight hours and reduce energy consumption.

Modern research suggests the energy savings are small or nonexistent, and some studies show energy use actually increases slightly in some regions. Despite this, the practice continues because changing it would require federal legislation, and there is no clear consensus on whether to keep daylight saving time year-round or switch to standard time year-round.

Some states have pushed for permanent daylight saving time, while others prefer permanent standard time. A few states have even held referendums on the issue. For now, the twice-yearly change remains the law in most of the US, with Hawaii and Arizona as the main exceptions.

Frequently Asked Questions

Do I need to change my phone or computer clock?

No. Phones and computers connected to the internet update automatically. If your device is offline, it may not update until you connect it to the internet or manually set the time. Older devices without internet access will need to be adjusted by hand.

What time should I change my clocks?

The official change happens at 2 a.m., but most people change their clocks the evening before going to bed. This way you wake up to the correct time. You can change them anytime between midnight and 2 a.m. without confusion.

Will my car update automatically?

Many newer cars with connected infotainment systems update automatically. Older cars and those without internet connectivity will not. Check your owner's manual or try adjusting the clock from your dashboard menu to see if it is automatic.

What states do not change their clocks?

Hawaii and most of Arizona do not observe daylight saving time and stay on standard time year-round. The Navajo Nation in Arizona does observe the change. US territories including Puerto Rico, Guam, and the US Virgin Islands also do not change.

Can I sleep through the time change without adjusting anything?

Yes, your body will adjust on its own over a few days. However, you may feel groggy or disoriented for a day or two, especially after the spring change. Adjusting your sleep schedule gradually in the days before the change can ease the transition.