Arizona operates primarily on Mountain Standard Time (MST) all year long. Unlike most of the United States, the state does not observe Daylight Saving Time (DST). This means that for part of the year, Arizona shares the exact same clock time as the Pacific Time Zone, and for the rest of the year, it matches Mountain Daylight Time.
Understanding Arizona's time schedule requires looking past a simple map. The state features notable exceptions, historical context, and unique quirks—especially regarding Native American reservations within its borders.
What Time Zone Does Arizona Follow?
For the majority of the state, Arizona sits in the Mountain Standard Time zone (UTC-7). Because the state legislature voted to exempt Arizona from the Uniform Time Act of 1966, clocks never move forward one hour in the spring or backward in the hour in the fall.
This policy creates a seasonal shift relative to the rest of the country:
- During Standard Time (November to March): Arizona shares the same time as Pacific Standard Time (PST) states like California, Nevada, and Washington.
- During Daylight Saving Time (March to November): Arizona shares the same time as Mountain Daylight Time (MDT) states like Colorado, Utah, and New Mexico.
The rationale behind this choice comes down to extreme summer temperatures and energy use.
Why Arizona Opted Out of Daylight Saving Time
The decision to stay on standard time permanently wasn't made on a whim. In 1968, two years after Congress passed the Uniform Time Act, Arizona lawmakers realized that springing forward would cause more harm than good.
The primary driver was climate. During scorching desert summers, an extra hour of evening sunlight meant people would run their air conditioning units longer into the evening when temperatures peaked. By keeping the sun setting earlier relative to the clock, homes could begin cooling down slightly sooner.
Furthermore, businesses and agricultural sectors worried about disrupted schedules. Cattle and crops operate on natural light cycles rather than legislative ones, and local commerce relied on predictable patterns that didn't need artificial clock tampering.
The Navajo Nation Exception
While the vast majority of Arizona skips DST, one major region does the exact opposite. The Navajo Nation, which spans northeastern Arizona as well as parts of New Mexico and Utah, does observe Daylight Saving Time.
This creates a complicated patchwork for travelers. If you drive through the Navajo Nation during the summer months, your phone will jump ahead one hour to match Mountain Daylight Time. If you cross back out into state or federal land managed by Arizona, your phone will drop back an hour.
To add another layer, the Hopi Reservation—which is completely surrounded by the Navajo Nation inside Arizona—does not observe DST. Residents and visitors on Hopi land stay on Mountain Standard Time year-round, matching the rest of Arizona.
Practical Impact on Travel and Business
For outsiders, Arizona's time zone status causes endless confusion, especially regarding virtual meetings, television broadcasts, and flights.
During the summer months (March through November), Phoenix, Tucson, and Flagstaff are on the exact same time as Los Angeles and San Francisco. If you schedule a call with someone in Phoenix in July, you treat them as if they are on Pacific Time.
During the winter months (November through March), Phoenix matches Denver time. If you call someone in Phoenix in January, you treat them as if they are on Mountain Time.
Airlines operating in Phoenix must adjust their published schedules relative to other states twice a year, even though local clocks don't move. Because neighboring states shift their time while Arizona stays put, flight connections through hubs like Phoenix Sky Harbor International Airport require careful attention during transition weeks.
Frequently Asked Questions
Does all of Arizona stay on standard time?
No. While almost all of the state skips Daylight Saving Time, the Navajo Nation in northeastern Arizona observes DST, matching the rest of the Navajo reservation in New Mexico and Utah.
Does Hawaii also skip Daylight Saving Time?
Yes. Alongside Arizona, Hawaii is the only other U.S. state that does not observe Daylight Saving Time. Because of its tropical location near the equator, day length varies very little throughout the year, making time changes unnecessary.
What time zone is Phoenix in during the summer?
During the summer, Phoenix is on Mountain Standard Time (MST), which puts it in sync with the Pacific Daylight Time (PDT) zone. Clocks in California and Arizona show the exact same time from March to November.
Why do some states still use Daylight Saving Time?
Daylight Saving Time was originally promoted to extend evening daylight during warmer months, theoretically saving energy and boosting evening retail commerce. However, modern studies debate whether energy savings actually occur, and several states continue to debate legislation to abolish the practice entirely.
