Which US states do not change their clocks?

Arizona and Hawaii. Arizona remains on Mountain Standard Time all year, except for the Navajo Nation, which does move its clocks. Hawaii remains on Hawaii Standard Time. Every other state observes the change from the second Sunday in March to the first Sunday in November.

Why does Arizona not observe daylight saving time?

Because an extra hour of summer evening sunlight is unwelcome in a desert climate. Later daylight means more air conditioning use rather than less, so Arizona exempted itself shortly after the national schedule took effect and has stayed on Mountain Standard Time ever since.

Does the Navajo Nation change its clocks?

Yes. The Navajo Nation observes daylight saving time throughout its territory, including the part inside Arizona, because it also extends into Utah and New Mexico and prefers a single internal clock. The Hopi Reservation, which lies within it, does not observe the change.

Can a state stay on daylight saving time permanently?

Not on its own. Federal law lets a state opt out of daylight saving and remain on standard time all year, but adopting permanent daylight time requires an act of Congress. That is why many state laws proposing year-round daylight time have been passed but never taken effect.

States That Don't Observe Daylight Saving

Every March most of the country loses an hour, but not all of it. The states that don't observe daylight saving stay exactly where they are, which means their relationship with every neighbouring clock quietly changes for eight months of the year. Anyone scheduling a call into Phoenix or Honolulu in July needs to know that.

This article covers which states don't observe daylight saving and why, the unusual exception inside Arizona, the territories that stay on standard time all year, and the federal law that permits an opt-out in the first place. To see how the exempt places line up against the rest right now, open the live US time board.

Which Are the States That Don't Observe Daylight Saving?

Arizona and Hawaii are the only two. Arizona keeps Mountain Standard Time all year, with the Navajo Nation as an exception, and Hawaii keeps Hawaii Standard Time. Every other state moves its clocks forward in March and back in November.

That short list is often misremembered as longer, partly because Indiana spent decades outside the system before joining it in 2006. The genuine holdouts among states that don't observe daylight saving have been constant since the late 1960s, when both took the exemption soon after it became available.

Why Arizona Opted Out

Arizona's reasoning was heat. In a desert summer the last thing most residents want is an extra hour of afternoon sun, since it pushes air conditioning demand later into the evening rather than saving energy. Moving the clock forward would mean cooling homes harder during the hottest part of the day and losing the cool early morning to the alarm clock.

The state briefly tried the change after the Uniform Time Act took effect, disliked it, and exempted itself. The practical result is that Arizona reads the same as California from March to November, then falls back into step with Colorado, Utah and New Mexico for the winter. If you rely on the Mountain Time clock to reach Phoenix in summer, you will be an hour out.

The Navajo Nation Exception

The Navajo Nation does observe daylight saving time, even in the Arizona portion of its territory, because the nation also extends into Utah and New Mexico and prefers one internal clock to three. Inside it sits the Hopi Reservation, which does not observe the change and therefore keeps Arizona time. The result is one of the strangest time maps in the country: a reservation on daylight time surrounding a reservation on standard time, inside a state that ignores the change entirely.

Why Hawaii Stays on Standard Time

Hawaii's reason is latitude. Close to the tropics the length of the day barely varies across the year, so shifting the clock buys almost no extra evening light and there is little to be gained from the disruption.

Hawaii Standard Time therefore holds at the same offset all year, which means the gap to the mainland changes with the seasons rather than staying fixed. In winter Honolulu is two hours behind Los Angeles and five behind New York; in summer it is three and six. The Alaska and Hawaii clock page shows both, and it is worth noting that Alaska, unlike Hawaii, does observe the seasonal change.

Do US Territories Observe Daylight Saving?

No. Puerto Rico and the US Virgin Islands remain on Atlantic Standard Time all year, Guam and the Northern Mariana Islands remain on Chamorro Standard Time, and American Samoa remains on its own standard time. None of them shifts in March.

Their reasoning matches Hawaii's, since all sit at low latitudes where seasonal daylight varies little. The consequence for Puerto Rico is neat: it matches Eastern Daylight Time in summer and sits an hour ahead of Eastern Standard Time in winter. The full picture is set out in the guide to time in US territories.

How Is a State Allowed to Opt Out?

The Uniform Time Act of 1966 created the national schedule and, in the same breath, allowed any state to exempt itself and remain on standard time. The choice belongs to the state legislature, not to Congress or the Department of Transportation.

The permission runs one way only, and this is the point most often missed in public debate.

Staying on standard time: A state may do this by its own law, which is exactly what Arizona and Hawaii did.
Adopting permanent daylight time: A state may not do this alone; it requires an act of Congress, which is why dozens of state bills have passed with no visible effect.
Split states: A state divided between two zones may exempt the portion in one zone and not the other, a provision added after Indiana's difficulties.
Territories: These sit outside the schedule under their own arrangements rather than by exemption from it.

Bills grouped under the name Sunshine Protection Act have repeatedly proposed making daylight time permanent for the whole country, which would end the argument by removing the change altogether. None has yet become law, so the list of states that don't observe daylight saving remains at two.

It is worth being clear about what the current rule actually is, since the exemption is only meaningful against it. Under the Energy Policy Act of 2005, clocks in the rest of the country move forward on the second Sunday in March and back on the first Sunday in November, in both cases at 2:00 a.m. local time. Arizona and Hawaii simply do nothing on those two mornings. Everything else about their time-keeping, including which zone they sit in, is unaffected and remains a matter for the Department of Transportation.

Working With the States That Don't Observe Daylight Saving

The exempt places do not have a fixed relationship with their neighbours, and that is the trap. Arizona is one hour behind Denver in summer but level with it in winter, while being level with Los Angeles in summer and an hour ahead of it in winter.

When arranging anything with the states that don't observe daylight saving, name the city rather than the abbreviation. "Nine in the morning, Phoenix time" cannot be misread; "nine Mountain" can. The same care applies during the changeover weekends themselves, which are explained in when daylight saving time starts and ends. Indiana's long experiment with exemption, and the mess it produced, is covered in Indiana time zone history.

Conclusion

The states that don't observe daylight saving are Arizona, apart from the Navajo Nation, and Hawaii, and the territories stay on standard time as well. Both states took the exemption offered by the Uniform Time Act of 1966 for sound local reasons: too much heat in one case, too little seasonal daylight in the other. The practical effect is that their offset from the rest of the country changes twice a year even though their clocks do not. Check every zone at once on the live US time board, or start from ustime.now.

States That Don't Observe Daylight Saving Time