Which US states don’t observe daylight saving time?
Two, plus several territories — and the consequence is that those places change which coast they match, twice a year, without touching a clock.
The short answer
Arizona and Hawaii. Plus the territories: Puerto Rico, the US Virgin Islands, Guam, American Samoa and the Northern Mariana Islands.
One exception inside an exception — the Navajo Nation, which extends into Arizona, does observe daylight saving, so part of Arizona changes while the rest does not.
The list
| Place | Year-round offset |
|---|---|
| Arizona (except the Navajo Nation) | UTC−7 |
| Hawaii | UTC−10 |
| Puerto Rico, US Virgin Islands | UTC−4 |
| Guam, Northern Mariana Islands | UTC+10 |
| American Samoa | UTC−11 |
Everywhere else in the United States observes it.
Why Arizona opted out
Arizona tried daylight saving in 1967 and abandoned it the following year. The reasoning was climate: in a desert state where summer afternoons routinely pass 40 °C, shifting an hour of daylight later into the evening extends the hottest part of the day and increases cooling demand. The saving that daylight saving is meant to produce runs backwards there.
Hawaii's reasoning is different and simpler — it sits close enough to the equator that day length barely varies through the year, so there is nothing to shift.
The consequence: they change which coast they match
This is the part that actually affects scheduling, and it is counter-intuitive.
Arizona sits on Mountain Standard Time permanently. Everyone around it moves. So:
- In winter, Arizona matches Denver, and is 2 hours ahead of New York.
- In summer, Denver has moved forward and Arizona has not — so Arizona now matches Los Angeles, and is 3 hours ahead of New York.
Same place, same clock, different relationship to both coasts depending on the month. A recurring meeting with a Phoenix colleague moves by an hour twice a year, and it is never Phoenix that caused it.
The Navajo Nation complication
The Navajo Nation observes daylight saving and spans parts of Arizona, Utah and New Mexico. Inside it sits the Hopi Reservation, which does not.
The practical result is that driving across parts of north-eastern Arizona in summer can take you through several changes of local time within an hour or two. The time zone database models this with separate zone identifiers, which is exactly why zone names rather than state names are the right identifier.
Scheduling against a non-observing place
The rule is the same as everywhere, but it matters more here:
Use the city, never the abbreviation. "MST" is correct for Phoenix all year but correct for Denver only in winter — the same three letters describing two different behaviours.
And put a note on any recurring meeting involving Arizona or Hawaii to re-check it at the March and November transitions, because those are the moments the gap moves without either party changing anything.
Related: Does Arizona observe daylight saving time? · Daylight saving vs standard time
Timezone: World Clock Widget
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Figures on this page are computed from the IANA time zone database. Last generated 2026-08-18.