Why Arizona Doesn’t Change Its Clocks (Except Where It Does)

While most Americans spring forward each March, Arizona stays put. The state observed daylight saving briefly under the Uniform Time Act of 1966, then exercised its legal right to opt out in 1968 — and has kept standard time ever since. The reasoning is written in the summer forecast: when Phoenix regularly exceeds 110°F (43°C), an extra hour of evening daylight isn’t a gift. Desert life happens after sunset; pushing sunset toward 9 PM would mean more waking hours in brutal heat and more air conditioning burned.

The practical effect is that Arizona changes time zones twice a year without moving. In winter it matches Mountain Standard Time, one hour ahead of California. In summer, while neighbors shift, Arizona effectively aligns with Pacific Daylight Time — same clock as Los Angeles. Anyone scheduling calls with Phoenix learns to ask which half of the year it’s.

Then comes the famous exception within the exception. The Navajo Nation, whose territory spans Arizona, Utah, and New Mexico, does observe daylight saving time — keeping one consistent clock across its three-state land. But the Hopi Reservation, entirely surrounded by Navajo land, follows Arizona and doesn’t. The result is a geographic doughnut: driving a straight line through northeastern Arizona in summer, a traveler can cross between DST and non-DST territory multiple times within a couple of hours, changing the clock at each boundary.

Hawaii is Arizona’s only full-state companion in opting out, for the opposite-sounding but related reason: near the tropics, day length barely varies through the year, so shifting clocks accomplishes nothing. US territories — Puerto Rico, Guam, American Samoa, and others — likewise skip the ritual.

Arizona’s experiment is increasingly cited in the national argument over abolishing clock changes altogether, as sleep scientists document the health costs of the twice-yearly shift. Whatever the country decides, Arizona’s answer has been stable for over half a century: pick a time and keep it.

The clocks at itsdately.com apply these local rules automatically — Phoenix, the Navajo Nation’s Window Rock, and Los Angeles each show their true current hour, whatever the season.

Arizona’s stance also reflects daylight saving’s tangled American history. National clock-changing began in 1918 as a wartime coal-saving measure, was repealed, returned in World War II as year-round “War Time,” then dissolved into local chaos — by the early 1960s, a bus ride from Ohio to West Virginia could cross seven time changes. The Uniform Time Act of 1966 standardized the dates but let states opt out entirely, the escape hatch Arizona took. Congress still revisits the question regularly, with “lock the clock” bills proposing permanent time in one direction or the other.

The economics behind clock politics have flipped over the century. Daylight saving’s original sales pitch was energy: more evening light, less lighting fuel. Modern studies find the savings negligible — lighting is now a sliver of consumption, and air conditioning in hot states can erase or reverse the gains, exactly Arizona’s argument. Today’s loudest lobbies are recreational: golf, retail, and barbecue industries historically favored extended evening daylight, while sleep scientists, schools, and morning commuters line up against dark 8 AM sunrises. The tug-of-war explains why reform bills pass one chamber and stall in the next.

Related on itsdately: Which Time Zone Has the Most People? · Daylight Saving Time 2027: Exact Dates for the US, UK and Europe · What Time Do Stock Markets Open Around the World?

Further reading: IANA Time Zone Database For readers asking “Why Arizona Doesn't Change Its Clocks (Except Where It Does)”, the answer comes down to the specific factors covered above.

Related read: From Milliseconds to Attoseconds: The Small Units of Time.