Why Doesn't Arizona Observe Daylight Saving Time?
Arizona is the only continental US state that does not observe daylight saving time. Here is the history of why, the surprising exception of the Navajo Nation, and how it affects business across the southwest.
The Quick Answer
Arizona does not observe daylight saving time because the state legislature voted to permanently exempt itself from DST in 1968. The reason was practical: Arizona is hot, the sun is intense, and the state did not want an extra hour of evening sunlight in the summer because that meant another hour of needing air conditioning. By staying on standard time year-round, Arizonans get an earlier sunset in the summer — which means cooler evenings, less air conditioning load, and (in pre-modern times) more comfortable working conditions. The decision has stayed in place for nearly 60 years and is unlikely to change.
A Bit of Background on DST
Daylight saving time was first widely adopted in the United States during World War I as an energy-saving measure. It was reintroduced during World War II, then made optional after the war, then standardized by the Uniform Time Act of 1966. That act required all states that observed DST to do so on the same dates and gave individual states the option to opt out entirely. In 1968, Arizona chose to opt out. Hawaii also opted out, as did several US territories. The other 48 states did not, and have continued observing DST since.
Why the Heat Argument Matters
Phoenix in July routinely sees daytime temperatures of 110°F or higher. The hottest hours of the day are typically 4:00 PM to 7:00 PM. If Arizona observed DST, the sun would not set until around 8:30 PM — meaning the punishingly hot late afternoon would extend deep into what would otherwise be the cooler evening. Without DST, the sun sets around 7:30 PM, giving people earlier relief from the heat and reducing the time the sun is overhead during peak air conditioning hours. In a state where energy use for cooling is enormous, the choice not to observe DST has measurable effects on both household budgets and the electrical grid.
What Time Zone Is Arizona Actually In?
Arizona is in the Mountain Time Zone (MST, UTC−7). This is the same zone as Colorado, Utah, Wyoming, and Montana — the other Mountain states. But because Arizona does not observe DST and those states do, Arizona is on the same clock as the other Mountain states from November to March, then on the same clock as Pacific states (California, Oregon, Washington) from March to November. This effectively means Arizona "switches" time zones twice a year by staying still while everyone else moves around it. From a Phoenix resident's perspective, Denver is one hour ahead in summer but the same time as Phoenix in winter, while Los Angeles is the same time as Phoenix in summer but one hour behind in winter.
The Navajo Nation Exception
There is one big exception within Arizona: the Navajo Nation, which covers a large part of northeastern Arizona, DOES observe daylight saving time. The reason is that the Navajo Nation extends into Utah, New Mexico, and parts of Arizona, and the tribal government wanted to maintain consistent time across the entire reservation. Since Utah and New Mexico observe DST, the Navajo Nation does too — even within Arizona's borders. This means you can drive across the Navajo Nation in summer and your car clock would technically be wrong by an hour depending on where you are. Confusingly, the Hopi Reservation is entirely surrounded by the Navajo Nation but does NOT observe DST, following Arizona state policy. So you can have a small enclave of MST inside a region of MDT inside a state of MST.
How This Affects Travel and Business
For travelers passing through Arizona, the time zone situation can be genuinely confusing. Driving from Phoenix to Albuquerque in summer, you cross into Mountain Daylight Time and lose an hour. Driving from Phoenix to Las Vegas, you stay in the same effective time zone (both are on UTC−7 in summer, even though one is "MST" and the other is "PDT"). For businesses with operations across Arizona and other Mountain states, this means schedules and meetings need careful labeling — "9 AM Phoenix time" can mean two different things depending on the season. Many companies just use Pacific time year-round to avoid the confusion.
Hawaii Does the Same Thing for Different Reasons
Hawaii also does not observe DST, but for a different reason. Hawaii is close to the equator (roughly 21 degrees north latitude), so daylight hours barely change throughout the year — the longest day is only about 1.5 hours longer than the shortest day. That means the entire premise of DST (shifting summer evening daylight) provides almost no benefit. Combined with Hawaii's relative isolation from the mainland US business calendar, there was no reason to observe DST. Hawaii has stayed on Hawaii Standard Time (HST, UTC−10) year-round since 1947.
Other US Areas That Skip DST
Beyond Arizona and Hawaii, other parts of the US that skip DST include all of the US territories: Puerto Rico (UTC−4), US Virgin Islands (UTC−4), Guam (UTC+10), Northern Mariana Islands (UTC+10), American Samoa (UTC−11). The reasoning is similar to Hawaii: these are tropical or near-tropical regions where seasonal daylight variation is small. Within the continental US, only Arizona (excluding Navajo) opts out. There are also small parts of Indiana, Kentucky, and other border states with unusual time arrangements, though all of those areas DO observe DST.
Will Arizona Ever Change?
There has been no serious political momentum to start observing DST in Arizona. If anything, the trend nationally has been the OTHER direction — the US Senate unanimously passed the Sunshine Protection Act in 2022, which would have ended the practice of changing clocks twice a year by making DST permanent year-round. The bill did not become law, but if it ever does, Arizona's permanent-MST policy would suddenly look more aligned with the national direction (though Arizona would still be on standard time, not daylight time). For now, expect Arizona to stay on Mountain Standard Time year-round indefinitely.
Practical Tips for Arizonans and People Calling Arizona
A few practical takeaways: When scheduling meetings with someone in Phoenix, double-check whether they are on PDT or MST in your local conversion — they switch effectively twice a year. When travelling to or from Arizona, your phone usually updates automatically, but laptops do not. The Navajo Nation's DST observance can confuse car GPS systems crossing the reservation in summer. And if you live in Arizona, your computer should be set to "America/Phoenix" — NOT "America/Denver" — because Phoenix is the IANA timezone identifier that correctly handles the no-DST rule.
Check Arizona Time on Clockzilla
Clockzilla has a dedicated Phoenix page (clockzilla.io/time/phoenix) showing the current Phoenix time, timezone, and what other US cities currently match its clock. The time-difference pages also handle the no-DST quirk correctly — for example, clockzilla.io/difference/new-york-to-phoenix shows the correct 2-hour difference in winter and 3-hour difference in summer. This is useful if you regularly schedule across Arizona and want a quick sanity check on the current time difference.
The Bottom Line
Arizona does not observe daylight saving time because the state opted out in 1968 to avoid extending the brutally hot late-afternoon sunshine into the evening. The only exception is the Navajo Nation, which observes DST to stay aligned with the rest of the reservation in Utah and New Mexico. Hawaii, US territories, and parts of a few other US areas also skip DST. Expect Arizona's policy to remain unchanged for the foreseeable future. For practical purposes, Arizona is on the same clock as Mountain states in winter and Pacific states in summer.
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