Tempe, Arizona operates on Mountain Standard Time (MST) year-round, maintaining a fixed offset of UTC-7. Unlike most of the United States, the city does not observe Daylight Saving Time (DST), meaning clocks never spring forward or fall back. This unique scheduling choice creates shifting time differences with other regions throughout the year, impacting everything from cross-country phone calls to flight bookings and remote work coordination.
Understanding how this time structure operates prevents scheduling errors, missed meetings, and confusion during seasonal changes. Whether you're planning a trip to Arizona State University or coordinating with teams across different states, knowing the mechanics of local timekeeping helps keep your schedule accurate.
Why Tempe Skips Daylight Saving Time
Most of the state of Arizona opted out of the Uniform Time Act of 1966, utilizing an exemption granted under federal law. The primary reason comes down to climate and energy usage.
During the scorching summer months, evening temperatures in the region remain exceptionally high. Pushing the clock forward would mean an extra hour of intense evening sunlight, forcing residents and businesses to run air conditioning units longer during peak heat hours. Keeping clocks on standard time ensures that the sun sets slightly earlier relative to standard human schedules, helping reduce overall cooling energy consumption.
State lawmakers also noted that shifting clocks twice a year offers little practical benefit for agricultural and daily commercial rhythms in desert environments. As a result, the state remains permanently anchored to standard time.
How Time Differences Shift Throughout the Year
Because Tempe stays on MST (UTC-7) year-round while many other states shift between standard and daylight times, the time gap between Tempe and the rest of the country changes biannually.
During the winter months—from early November to mid-March—the entire United States aligns on standard time. During this period:
- Eastern Time (EST): Tempe is exactly 2 hours behind New York.
- Central Time (CST): Tempe is 1 hour behind Chicago.
- Mountain Time (MST): Tempe shares the exact same time as Denver (when Denver is off DST).
- Pacific Time (PST): Tempe is 1 hour ahead of Los Angeles.
During the summer months—from mid-March to early November—regions observing DST move their clocks forward by one hour to UTC-6 or UTC-5. Because Tempe does not move its clocks, the offset shifts:
- Eastern Daylight Time (EDT): Tempe becomes 3 hours behind New York.
- Central Daylight Time (CDT): Tempe becomes 2 hours behind Chicago.
- Mountain Daylight Time (MDT): Tempe becomes 1 hour behind Denver.
- Pacific Daylight Time (PDT): Tempe matches Pacific Time identically. During summer, clock times in Phoenix, Tempe, and Los Angeles read the exact same hour, even though Tempe remains on Mountain Standard Time.
Practical Impact on Travel and Business
The lack of seasonal clock changes frequently catches travelers and remote workers off guard. A virtual meeting scheduled for 10:00 AM in May with a colleague in New York means one thing in winter and another in summer.
Airlines, train networks, and major logistics companies operating within Tempe adjust their operations manually against national schedules. When booking flights through US Department of Transportation guidelines or checking itineraries, ticket times reflect local clock readings, but connecting flights in states that observe DST require careful mental math.
Remote professionals working with clients in states like California or New York must double-check meeting slots during the spring and autumn transition weeks. Software calendars like Google Calendar or Microsoft Outlook usually handle timezone conversions automatically, provided the location settings for Tempe are configured correctly to use the America/Phoenix IANA time zone identifier, which has no DST rules applied.
Exceptions Within Arizona
While Tempe and the vast majority of Arizona ignore Daylight Saving Time, exceptions exist within state boundaries that travelers should note.
The Navajo Nation, located in northeastern Arizona, spans parts of Utah and New Mexico and chooses to observe Daylight Saving Time. If you cross from standard Arizona territory into Navajo lands during the summer, you must push your watch forward by one hour. Conversely, the Hopi Reservation—which is entirely surrounded by the Navajo Nation—does not observe DST, sticking strictly to Arizona's standard time. This creates localized time zone boundaries where neighboring towns operate an hour apart for part of the year. However, Tempe sits in Maricopa County in the central part of the state, far away from these tribal land variations.
Frequently Asked Questions
Does Tempe ever change its clocks?
No. Tempe stays on Mountain Standard Time (UTC-7) all year and never participates in Daylight Saving Time.
Why does Arizona match California time in the summer?
During summer, Pacific states move forward to Pacific Daylight Time (UTC-7). Because Arizona stays on Mountain Standard Time (UTC-7), its static offset matches the summer offset of the Pacific zone.
What is the official time zone identifier for Tempe?
Computer systems and world clock databases track Tempe using the America/Phoenix time zone identifier, which explicitly excludes DST rules.
Do all parts of Arizona ignore Daylight Saving Time?
No. The Navajo Nation in northeastern Arizona observes DST, creating an exception to the statewide rule. Tempe, however, follows the standard non-DST exemption.
