The Heat Argument
Arizona's refusal to observe Daylight Saving Time comes down to a single, practical fact: the state is extraordinarily hot. Phoenix regularly records summer temperatures exceeding 110°F (43°C), and the summer of 2023 saw 31 consecutive days above 110°F — a record. Adding an extra hour of afternoon daylight to an already brutal desert summer was, and remains, deeply unpopular.
The logic is simple. Daylight Saving Time shifts daylight from morning to evening. In most temperate states, this means longer, pleasant evenings in summer. In Arizona, it means an extra hour of scorching afternoon sun when residents are trying to be outdoors, drive home from work, or simply survive. Air conditioning costs are already among the highest in the nation. An extra hour of peak-heat daylight would mean higher energy bills and greater strain on the electrical grid.
"We have so much daylight here already. Why would we want more of it at the end of the hottest part of the day?"
— Common sentiment among Arizona residents
The Legal Basis
Arizona's DST exemption is entirely legal under federal law. The Uniform Time Act of 1966 established Daylight Saving Time across the United States but included an explicit provision allowing individual states to opt out by passing a state law. Arizona did exactly this in 1968, just two years after the Act passed.
The other state with a similar exemption is Hawaii, which also does not observe DST — for the same reason as Arizona. Hawaii is so close to the equator that seasonal daylight variation is minimal (about 1.5 hours between the longest and shortest days), making DST functionally pointless. Hawaii also switched permanently in 1967.
Several US territories — including Puerto Rico, Guam, American Samoa, the US Virgin Islands, and the Northern Mariana Islands — also do not observe DST.
How Arizona's Time Compares Throughout the Year
| Season | Arizona (MST) | California (PT) | Colorado (MT) | New York (ET) |
|---|---|---|---|---|
| Summer (DST active elsewhere) | UTC−7 | UTC−7 (PDT) | UTC−6 (MDT) | UTC−4 (EDT) |
| Winter (standard time) | UTC−7 | UTC−8 (PST) | UTC−7 (MST) | UTC−5 (EST) |
Notice something striking: in summer, Arizona is on the same time as California — despite being geographically east of it. And in winter, Arizona matches Colorado. Arizona effectively shifts its relative position to the rest of the country twice a year without changing its own clocks at all.
The Navajo Nation Exception — and the Hopi Within It
Here is where Arizona's timezone situation becomes genuinely extraordinary. Covering a vast stretch of northeastern Arizona (as well as parts of Utah and New Mexico), the Navajo Nation is a federally recognized sovereign tribal territory. As a sovereign nation, it sets its own laws — including its own timezone rules.
The Navajo Nation does observe Daylight Saving Time. This means that in summer, driving from Flagstaff into the Navajo Nation requires setting your clock forward one hour. Leaving the Navajo Nation back into the rest of Arizona requires setting it back again.
But it gets stranger. Completely surrounded by the Navajo Nation in northeastern Arizona is the Hopi Reservation — another sovereign territory. The Hopi do not observe DST, matching the rest of Arizona. So the full sequence when crossing the region in summer is:
A driver crossing all these zones on a single road trip in summer would need to change their clock up to seven times during a journey through northeastern Arizona. It is arguably the most complex local timezone situation in the world for a relatively small geographic area.
The Ongoing DST Debate in Arizona
Arizona's DST exemption is not without controversy. The tourism industry has repeatedly argued that being out of sync with the rest of the country costs the state in lost business. California and Nevada — major sources of visitors — move their clocks, and the resulting time confusion reduces cross-border tourism. Major sports leagues and television networks must account for Arizona's permanent MST when scheduling broadcasts.
Several bills have been introduced in the Arizona legislature over the years to adopt permanent DST or rejoin the national standard. All have failed. The heat argument remains decisive for most Arizona voters, and a 2020 poll found that 55% of Arizonans preferred to stay on permanent standard time — similar to the national conversation about simply abolishing DST altogether.
There is also an ironic twist: if the US Congress were to pass legislation making Daylight Saving Time permanent year-round nationwide (a measure that has been proposed multiple times), Arizona would have to comply — and would end up being the only state that actually preferred the time it would be forced to adopt.