Do All US States Observe Daylight Saving Time?

Most Americans are very familiar with the routine for Daylight Saving Time -- set the clock forward by an hour in March so there’s more daylight in the evening to enjoy in the warmest part of the year, and then move it back in November. Most U.S. states observe DST, but there are exceptions, namely Arizona, Hawaii, and the U.S. territories. Arizona has calculated that it saves millions in cooling costs by staying on Mountain Standard Time all year, so the state opted out of the federal standard in 1967.

However, the Navajo Nation, located in the northeastern corner of Arizona, does follow Daylight Saving Time, making it the only part of Arizona that changes its clocks. The semi-autonomous territory covers 27,425 square miles (71,030 sq km), and extends into parts of Utah and New Mexico, both of which observe DST. The Navajo Nation's rationale was that it would be better to have one standard time for the entire Navajo community.

Saving daylight, but not everywhere:

• To complicate matters further, the Hopi Reservation, an enclave located entirely within the Navajo Nation, does not observe DST, just like the rest of Arizona.
• Because of Hawaii’s tropical latitude, there’s not much variation in the amount of daylight between winter and summer, so that state doesn’t change its clocks either.
• The Navajo Nation is the largest reservation in the United States, covering an area roughly the size of West Virginia.