Mountain Standard Time (MST) · UTC−7 · Year-round · No Daylight Saving Time · Navajo Nation exception
Arizona (MST, UTC-7) never changes. The time difference with other zones shifts when they observe DST.
| Zone | Winter (Standard) | Summer (Daylight) |
|---|---|---|
| Eastern (ET) | +2 hrs | +3 hrs |
| Central (CT) | +1 hr | +2 hrs |
| Mountain (MT) | Same | +1 hr |
| Pacific (PT) | −1 hr | Same |
| Alaska (AKT) | −2 hrs | −1 hr |
| Hawaii (HST) | −3 hrs | −3 hrs |
Example: When it is 12:00 PM MST in Phoenix, it is 2:00 PM EST (3:00 PM EDT) in New York.
Arizona opted out of Daylight Saving Time under the Uniform Time Act of 1966. With summer temperatures regularly exceeding 110°F (43°C) in Phoenix, residents preferred cooler evening hours over an extra hour of scorching afternoon sun.
Arizona and Hawaii are the only two US states that do not observe DST. Arizona stays on MST (UTC-7) year-round. This means in summer, Arizona matches Pacific Daylight Time (California), and in winter it matches Mountain Standard Time (Colorado).
The practical effect: Arizonans never change their clocks. But the time difference between Arizona and states that do observe DST shifts twice a year — in March (spring forward) and November (fall back).
The Navajo Nation in northeastern Arizona is the exception. It spans 27,000 square miles across Arizona, Utah, and New Mexico — and observes Daylight Saving Time like the rest of the Mountain Time Zone (America/Denver).
Even more unusual: the Hopi Reservation, which is completely surrounded by Navajo land, does not observe DST. This creates a rare “time zone donut” — driving through northeastern Arizona, you could change time zones multiple times.