Why Doesn't Arizona Observe Daylight Saving Time?

Arizona adopted daylight saving briefly in 1967 under the newly-passed Uniform Time Act, then exempted itself the very next year under a provision that lets states opt out entirely. It has stayed on standard Mountain Time year-round ever since.

The commonly cited reason is Arizona's extreme summer heat. Shifting clocks forward would mean an extra hour of scorching evening sunlight rather than an extra hour of cooler darkness — undesirable in a state where summer highs regularly exceed 100°F.

Keeping fixed Mountain Standard Time also means Arizona's clocks match Pacific Time every summer (since Pacific zones spring forward while Arizona doesn't) and Mountain Time every winter — a quirk that can confuse travelers.

The Navajo Nation, which extends into northeastern Arizona (as well as Utah and New Mexico), does observe daylight saving time, aligning with its larger multi-state footprint rather than the rest of Arizona. This creates the unusual situation where two neighboring communities in Arizona can be an hour apart for part of the year.

Anyone scheduling a call or flight between Phoenix and a Mountain zone city like Denver needs to check the calendar: the two cities share the same clock in winter but are an hour apart for roughly eight months of the year once Colorado springs forward and Arizona doesn't.

The same applies in reverse with Pacific zone cities — Phoenix and Los Angeles are an hour apart in winter but share the exact same clock time from March through early November, a pattern that regularly surprises people unfamiliar with Arizona's exemption.

Airlines, delivery services, and national retailers operating in Arizona build this seasonal flip into their scheduling systems automatically, but individuals coordinating one-off meetings or calls are the ones most likely to get caught out by it.