States That Do Not Change Clocks for Daylight Saving Time
Most of Arizona and all of Hawaii do not follow seasonal daylight saving changes. Learn the Navajo Nation exception and US territory rules.
Daylight Saving Time (DST) is a seasonal practice that shifts clocks forward by one hour to extend evening daylight. While most U.S. states observe DST, two states—Arizona and Hawaii—are commonly cited as not participating. However, the situation is more nuanced: Arizona’s Navajo Nation does observe DST, and the U.S. territories also have distinct rules. Understanding these exceptions clarifies why the simple answer of “two states” is incomplete and helps travelers, businesses, and residents navigate time‑keeping across the country.
The two states generally associated with no DST
Arizona and Hawaii are the only U.S. states that do not observe Daylight Saving Time across their entire territories. Arizona’s decision stems from its hot climate; keeping clocks on Mountain Standard Time year‑round reduces the need for late‑morning light and helps conserve energy. Hawaii’s geographic location near the equator means daylight hours vary little throughout the year, so a time shift offers minimal benefit. Consequently, residents and businesses in these states operate on a single time standard all year, simplifying scheduling but requiring adjustments when interacting with partners in DST‑observing regions. The absence of DST in these states is codified in federal law: the Uniform Time Act of 1966 allows states to opt out, and both Arizona and Hawaii have exercised that option. This legal framework ensures consistency for federal agencies, transportation schedules, and interstate commerce.
Why most of Arizona stays on standard time
Arizona’s statewide non‑observance of DST is largely due to its extreme summer temperatures. By remaining on Mountain Standard Time year‑round, the state avoids the late‑afternoon heat that would accompany a DST shift. This policy also aligns with the preferences of many residents who value consistent daylight hours for outdoor activities and energy savings. The only region in Arizona that does observe DST is the Navajo Nation, which spans parts of Arizona, New Mexico, and Utah. The Navajo Nation follows DST to maintain uniformity with neighboring states and to support economic ties that rely on synchronized business hours. This exception is mandated by the Navajo Nation’s own legal statutes and is recognized by federal time‑keeping authorities. As a result, travelers and businesses must be aware that a single state can contain both DST‑observing and non‑observing areas, necessitating careful time‑zone planning when crossing the Navajo Nation boundary.
How the Navajo Nation exception works
The Navajo Nation, which spans parts of Arizona, New Mexico, and Utah, is the only area in the United States that observes daylight saving time (DST) while the surrounding state territories do not. This unique arrangement originates from the 1997 Navajo Nation Legislature decision to adopt DST to align with neighboring communities and improve economic and social coordination. The Navajo Nation’s own government sets the start and end dates for DST, matching the federal schedule: clocks move forward one hour on the second Sunday in March and back one hour on the first Sunday in November. Consequently, residents living in the Navajo Nation’s Arizona portion must adjust their clocks, while those in the rest of Arizona remain on Mountain Standard Time year‑round. The exception is strictly limited to the Navajo Nation’s jurisdiction; the Hopi Reservation, which lies entirely within the Navajo Nation’s geographic area, does not observe DST, creating a second, smaller time‑keeping enclave. This patchwork of time rules requires travelers and businesses to be mindful of local jurisdiction when scheduling appointments or coordinating transportation across the region.
Why Hawaii does not change clocks
Hawaii’s decision to forgo daylight saving time dates back to the 1960s, when the state legislature voted to remain on Hawaii Standard Time (HST) throughout the year. The primary rationale was economic: the state’s tourism industry, which relies on consistent daylight hours for visitors, found that the time shift caused confusion and reduced daylight for beach and resort activities. Additionally, Hawaii’s geographic latitude results in relatively consistent daylight duration across seasons, diminishing the perceived benefits of DST. The state’s government has repeatedly reaffirmed its stance, citing studies that show minimal energy savings and potential health impacts from the biannual clock change. As a result, Hawaii remains on HST (UTC‑10) all year, providing a stable time reference for residents, businesses, and visitors. This consistency simplifies scheduling for international travelers and supports the state’s focus on tourism and hospitality, where predictable daylight is a key asset.
US territories that also do not observe DST
The United States has several territories that, like the two states of Arizona and Hawaii, do not observe daylight saving time (DST). The most notable among these is the Commonwealth of Puerto Rico, which remains on Atlantic Standard Time (AST) year‑round, staying two hours ahead of Eastern Standard Time. This policy aligns with the island’s preference for consistency in business and tourism schedules, avoiding the biannual clock changes that can disrupt flight itineraries and local commerce. Similarly, the U.S. Virgin Islands, located in the Caribbean, also stay on AST throughout the year. The U.S. Minor Outlying Islands, such as the Northern Mariana Islands, also maintain a single time zone without DST adjustments, although their small populations and remote locations mean the impact is limited to local administrative matters. These territories’ decisions are codified in federal statutes and local legislation, ensuring that residents and visitors experience a stable time reference regardless of the season. The consistent timekeeping in these territories simplifies scheduling for international trade, aviation, and telecommunications, which rely on fixed offsets for coordination across multiple jurisdictions.
How to check time when traveling between observing and nonobserving areas
When planning travel that crosses between DST‑observing and non‑observing regions, it is essential to verify the current offset for each location. A reliable method is to consult the National Institute of Standards and Technology (NIST) time zone database, which provides authoritative UTC offsets for all U.S. jurisdictions, including the exceptions in Arizona, Hawaii, and the territories. For example, a trip from Phoenix (no DST) to Denver (observes DST) requires a one‑hour adjustment when DST begins in Colorado, but no change when the traveler returns to Phoenix. Travelers can also use reputable online time‑zone converters that automatically account for DST transitions, but they should cross‑check with official sources during periods of change, such as the second Sunday in March and the first Sunday in November. Additionally, many modern smartphones and smartwatches automatically update to the correct local time when the device’s location services detect a change in time zone; however, users should verify that the device’s time‑zone database is current, especially after major software updates. For business travelers, scheduling meetings across time zones can be simplified by using calendar tools that display both local and UTC times, ensuring that all participants remain synchronized regardless of DST observance.
