Flagstaff, Arizona operates on Mountain Standard Time (MST) year-round, sitting at UTC-7. Unlike the vast majority of the United States, Flagstaff and most of Arizona do not observe Daylight Saving Time (DST). When the rest of the country adjusts clocks forward in the spring and back in the autumn, your clocks in Flagstaff stay exactly where they are.
This policy creates shifting time relationships with neighboring states. For half the year, Flagstaff shares a time zone with Pacific Daylight Time states like California, while during the winter months, it matches Mountain Time states like Colorado. Understanding these shifts prevents missed flights, scheduling errors, and confusion during cross-country calls.
Flagstaff Time Zone Basics
Flagstaff is located in Coconino County, northern Arizona. The region follows Mountain Standard Time continuously. It doesn't use Mountain Daylight Time (MDT) (UTC-6).
- Standard Time Offset: UTC-7
- Observes DST: No
- Primary Identifier: MST (Mountain Standard Time)
Because the city stays on standard time indefinitely, the offset between Flagstaff and Coordinated Universal Time never changes. It remains seven hours behind UTC 365 days a year.
Why Arizona Opted Out of Daylight Saving Time
The state legislature voted to exempt Arizona from the Uniform Time Act of 1966, officially adopting year-round standard time in 1968. The decision stemmed primarily from regional geography and climate.
During peak summer months, northern and southern Arizona experience intense heat. If the state observed DST, sunsets during July would occur around 8:00 PM or later instead of an hour earlier. Residents would face stifling outdoor temperatures late into the evening, driving up residential air conditioning loads and energy consumption. Keeping clocks unchanged ensures that businesses and households experience earlier evening cooling.
For more details on national timekeeping standards and federal exemptions, check the U.S. Department of Transportation time zone guidelines.
The Navajo Nation Exception
If you travel just east or northeast of Flagstaff into the Navajo Nation, the rules change completely. The Navajo reservation spans parts of Arizona, New Mexico, and Utah, and it observes Daylight Saving Time to maintain consistent timekeeping across its entire multi-state territory.
Meanwhile, the Hopi Reservation, which sits entirely as an enclave inside the Navajo Nation near Flagstaff, does not observe DST, matching the rest of Arizona. Driving through northern Arizona can mean crossing multiple time boundaries within a short distance during the spring and summer months.
How Flagstaff Time Compares Across the US
Because neighboring regions shift their clocks while Flagstaff stays put, the time difference between Arizona and the rest of the country fluctuates twice a year.
- Summer (Mid-March to Early November): When California, Nevada, and Washington are on Pacific Daylight Time (PDT, UTC-7), they share the exact same time as Flagstaff. Simultaneously, Colorado and Utah switch to Mountain Daylight Time (MDT, UTC-6), putting them one hour ahead of Flagstaff.
- Winter (Early November to Mid-March): When the rest of the country returns to standard time, the Pacific states drop to UTC-8 (one hour behind Flagstaff), while Mountain Time states drop to UTC-7 (matching Flagstaff's time).
For a complete historical breakdown of regional timekeeping laws, consult Wikipedia's time in Arizona overview.
Common Scheduling Mistakes to Avoid
Managing appointments, remote meetings, and travel itineraries across state lines during seasonal changes often causes mix-ups.
- Assuming uniform Mountain Time: Don't assume Colorado and Arizona share an offset in July. Colorado is an hour ahead during summer.
- Forgetting Navajo Nation rules: If you have meetings with tribal offices or businesses inside the Navajo Nation between March and November, remember their clocks are set one hour ahead of Flagstaff.
- Hardcoding calendar apps: Relying on automated software without checking timezone settings can cause scheduling errors when syncing events with devices located in states that observe DST.
Frequently Asked Questions
Does Flagstaff ever change its clocks?
No. Flagstaff has maintained year-round Mountain Standard Time without seasonal shifts for decades.
Is Arizona the only state that doesn't observe DST?
Hawaii also stays on standard time year-round. Several U.S. territories, including Puerto Rico, Guam, and the U.S. Virgin Islands, also skip the biannual time change.
What time zone is Flagstaff in during the summer?
Flagstaff remains in Mountain Standard Time (MST, UTC-7) all summer, even though neighboring states switch to daylight saving time.
Why do some parts of Arizona observe DST while Flagstaff doesn't?
The Navajo Nation spans three states and chose to adopt DST to unify its administrative schedule across state lines. Flagstaff and Coconino County follow the statewide exemption.
