Why doesn't Arizona change clocks?

The state legislature concluded that evening daylight in a desert summer increases air conditioning demand. DST's promised energy savings reversed under that heat load, so Arizona used the Uniform Time Act's opt-out provision and has stayed on MST since 1967.

Is Arizona on Pacific Time in summer?

No. Arizona stays on Mountain Standard Time (UTC−7) year-round. In summer, MST shares an offset with Pacific Daylight Time (UTC−7), so clocks match Los Angeles. Arizona has not adopted the Pacific zone.

Does the Navajo Nation observe DST?

Yes. The Navajo Nation follows the US DST schedule: second Sunday in March to first Sunday in November. It runs on MDT (UTC−6) during that window to keep a single time across its territory in Arizona, Utah and New Mexico.

Does the Hopi Reservation observe DST?

No. The Hopi Reservation, entirely enclosed by the Navajo Nation, stays on MST year-round. In summer it forms a standard-time island inside the Navajo daylight-time perimeter.

What time zone is Phoenix in?

Phoenix is on Mountain Standard Time (UTC−7) all year. The city never changes its clocks.

When does DST start and end in the Navajo Nation?

The Nation follows the federal schedule: clocks spring forward on the second Sunday in March and fall back on the first Sunday in November. During that period the Nation is on MDT (UTC−6), one hour ahead of the rest of Arizona. --- ## The Bottom Line Arizona keeps Mountain Standard Time while the country dances around it. In winter it matches Denver. In summer it matches Los Angeles. The Navajo Nation breaks ranks and observes DST to unify its cross-state territory. The Hopi Reservation breaks ranks with the Navajo, holding to standard time inside a daylight-time doughnut. The next time the clocks change, most of Arizona will not move. If you are driving through the Four Corners, check your phone, check the road signs and, when in doubt, ask.

Does Arizona Observe Daylight Saving Time?

Most of Arizona locks its clocks to Mountain Standard Time and leaves them there. Phoenix, Tucson, Flagstaff and nearly every other community skip the spring-forward, fall-back ritual entirely. The result is a state that matches Denver in January and Los Angeles in July, with two glaring exceptions that turn a Four Corners road trip into a time-zone obstacle course.

The Short Answer: Most of Arizona Stays Put

Arizona runs on Mountain Standard Time (MST, UTC−7) all twelve months. No clock changes, ever.

The complication arrives with the Navajo Nation, which spans Arizona, Utah and New Mexico. The Nation observes daylight saving time. Inside its boundaries sits the Hopi Reservation, which does not. Drive from Flagstaff to Tuba City in summer and you add an hour. Cross the Hopi mesas on the same trip and you lose it again, then regain it on the far side. Even long-time residents double-check.

Arizona and Hawaii are the only two states that skip DST entirely.

Why Arizona Said No: Air Conditioning, Not Agriculture

Arizona last sprang forward in 1967. The Uniform Time Act of 1966 had just taken effect, and the state legislature ran the numbers. An extra hour of evening sun in Phoenix meant an extra hour of air conditioning load when temperatures were still punishing. The standard DST sales pitch (shift daylight to the evening when people are active) collapses when the evening is the worst time to be outside. More sunlight after dinner meant higher electricity bills and more strain on the grid, not less.

So lawmakers used the opt-out clause written into the Uniform Time Act. The state has stayed on MST ever since.

What Time Arizona Actually Keeps

Arizona sits in the Mountain zone but ignores Mountain Daylight Time.

Winter (November to March): Arizona is on MST (UTC−7). Denver, Salt Lake City and Albuquerque are also on MST. Clocks match.

Summer (March to November): Arizona remains on MST (UTC−7). Denver and the rest of the Mountain zone jump to MDT (UTC−6). Arizona is now an hour behind them.

That seasonal flip is the source of most confusion. In July, noon in Phoenix is 1 p.m. in Denver. In January, noon is noon in both cities.

Summer Alignment: MST Equals Pacific Daylight Time, but Arizona Is Not on Pacific Time

The shorthand "Arizona is on Pacific time in summer" is wrong and useful at the same time. Here is the breakdown:

Pacific Daylight Time (PDT): UTC−7
Mountain Standard Time (MST): UTC−7

When Los Angeles observes PDT, its clocks match Phoenix. But Arizona has not joined the Pacific zone. It simply holds MST, and MST happens to share an offset with PDT from mid-March to early November. When California falls back to Pacific Standard Time (UTC−8) in November, Arizona stays at UTC−7 and pulls an hour ahead again.

The mental model: Arizona is UTC−7, period. The rest of the continent shifts around it.

The Navajo Nation: Why Part of Arizona Springs Forward

The Navajo Nation covers portions of northeastern Arizona, southeastern Utah and northwestern New Mexico. It observes DST on the full US schedule: second Sunday in March to first Sunday in November. During those months the Nation runs on MDT (UTC−6), one hour ahead of the surrounding Arizona landscape.

The reason is territorial coherence. Because the Nation crosses into Utah and New Mexico (both DST-observing states), keeping a single time across all three segments avoids fragmenting government services, school schedules and commerce. The result for an Arizona driver: the 75-mile stretch from Flagstaff to Tuba City crosses a time-zone boundary.

The Hopi Reservation: Standard Time Inside Daylight Time

The Hopi Reservation sits entirely inside the Navajo Nation. It does not observe DST.

In summer the layers stack like this:

Arizona outside the Navajo Nation: MST (UTC−7)
Navajo Nation: MDT (UTC−6)
Hopi Reservation (inside the Navajo perimeter): MST (UTC−7)

A drive from one side of the Navajo Nation to the other can cross the Hopi mesas and require two clock changes. The Hopi stay on standard time year-round, just like the rest of Arizona beyond the Navajo boundary. A pocket of MST wrapped in MDT, wrapped in MST again.

How to Know What Time It Is in Arizona Right Now

Let the phone figure it out. Most devices use location and will display correct local time automatically. Near the Navajo or Hopi boundaries, cellular pings can drift. Check manually if the displayed time does not match the landscape.

Memorise the offset. Arizona is UTC−7, always. If you know your own UTC offset, the arithmetic is trivial.

Winter rule. Arizona equals Denver. Noon in Colorado is noon in Phoenix.

Summer rule. Arizona equals Los Angeles. Noon in California is noon in Phoenix. Denver is an hour ahead.

Near the Four Corners, ask. Time-zone boundaries cut through gas stations, trading posts and motels. A wrong assumption costs you a meeting or a meal.

Arizona Against Its Neighbours Through the Year

Winter (standard time): - Arizona (MST, UTC−7) equals Denver (MST, UTC−7) - Arizona is one hour ahead of Los Angeles (PST, UTC−8) - Arizona equals Salt Lake City (MST, UTC−7)

Summer (daylight time): - Arizona (MST, UTC−7) equals Los Angeles (PDT, UTC−7) - Arizona is one hour behind Denver (MDT, UTC−6) - Arizona is one hour behind Salt Lake City (MDT, UTC−6)

Arizona aligns with its Mountain neighbours only in winter. Come March, it syncs with the West Coast instead.