Arizona is one of the only places in the continental United States where you can drive across an internal border and gain or lose an hour — not because you've crossed a time zone line on the map, but because you've crossed into land that follows a different rule about Daylight Saving Time.
Arizona sits on Mountain Time, but doesn't spring forward
Officially, the entire state of Arizona is in the Mountain Time Zone. But under the Uniform Time Act of 1966, states are allowed to opt out of observing Daylight Saving Time (they just can't choose to stay on permanent DST instead). Arizona made that choice back in 1968, and has stayed on Mountain Standard Time (UTC-7) year-round ever since.
The practical effect: for about eight months of the year — whenever the rest of the Mountain Time Zone springs forward — Arizona's clocks stay put. That means Arizona effectively matches Pacific Daylight Time (California, Nevada, Washington) during the summer, and switches to matching Mountain Standard Time neighbors like Utah and New Mexico during the winter, without ever changing its own clocks at all.
Why Arizona opted out
Arizona actually did try Daylight Saving Time first. When the Uniform Time Act of 1966 standardized DST nationally, Arizona went along with it — observing DST from April to October 1967, like most of the rest of the country.
The backlash was immediate, and specifically about air conditioning. In most of the US, the logic behind DST was that an extra hour of evening daylight would reduce electricity use for lighting and heating. In Arizona, it worked in reverse: that same extra hour of evening daylight meant homes and businesses stayed hot for longer into the part of the day when people were actually awake and running their air conditioners, pushing cooling costs up rather than down. Farmers, whose schedules run by the sun rather than the clock, didn't benefit either, and parents objected to children being out in the heat an hour later before sunset.
Arizona Governor Jack Williams signed the state's opt-out into law on March 21, 1968, with overwhelming legislative support — the bill passed the state Senate 25 to 3 and the House 49 to 1. That law, Arizona Revised Statutes §1-242, has never been amended since.
Except the Navajo Nation
Here's the twist: the Navajo Nation, which covers a large area in northeastern Arizona (and extends into Utah and New Mexico), does observe Daylight Saving Time — specifically so its own clocks stay aligned with the Navajo Nation land in neighboring states, rather than with the rest of Arizona. So from spring to fall, most of Arizona is an hour behind the Navajo Nation, despite being in the same state.
It gets one layer more complicated still: the Hopi Reservation, which is entirely surrounded by Navajo Nation land, does not observe DST — so it stays aligned with the rest of Arizona instead, creating a small "island" of standard time inside the DST-observing Navajo Nation.
What this actually means if you're calling or visiting
- March to November: Phoenix, Tucson, and most of Arizona match Pacific Time. The Navajo Nation is an hour ahead, matching Mountain Time.
- November to March: All of Arizona (including the Navajo Nation) matches Mountain Time — everyone's back on the same clock.
- If you're navigating between Flagstaff and somewhere like Monument Valley or Antelope Canyon, you may be crossing this line without any obvious signage — worth double-checking before a scheduled tour or reservation.
If you need the exact current time in Phoenix, or want to compare it against a city elsewhere, the time zone converter always reflects each location's real current offset — including Arizona's DST-free status — rather than assuming every place in a time zone behaves the same way.
Frequently asked questions
Is Arizona on Mountain Time or Pacific Time?
Officially, all of Arizona is in the Mountain Time Zone, on Mountain Standard Time (UTC−7) year-round. But because it never springs forward, Arizona effectively matches Pacific Daylight Time — California, Nevada, Washington — from March to November, then matches Mountain neighbours like Utah and New Mexico in winter.
Why did Arizona stop observing Daylight Saving Time?
Air conditioning. Arizona tried DST from April to October 1967 and the backlash was immediate. An extra hour of evening daylight kept homes and businesses hot later into the part of the day when people were awake and running their AC, pushing cooling costs up rather than down.
Does the Navajo Nation change its clocks?
Yes. The Navajo Nation covers a large area of northeastern Arizona and extends into Utah and New Mexico, and it observes Daylight Saving Time so its clocks stay aligned across all three states rather than with the rest of Arizona. From spring to autumn it runs an hour ahead of Phoenix.
What law lets Arizona skip Daylight Saving Time?
The Uniform Time Act of 1966 allows states to opt out of DST, though it does not let them stay on permanent DST instead. Governor Jack Williams signed Arizona's opt-out on 21 March 1968. That law, Arizona Revised Statutes §1-242, has never been amended since.