Arizona does not observe Daylight Saving Time mainly because of historical reasons tied to extreme heat and energy use. In 1967 the state opted out of the federal DST schedule, keeping standard time year-round. The reasoning was that an extra hour of daylight in the evening would keep homes and businesses cooler later, which would actually raise air-conditioning needs and energy consumption, making the time change counterproductive for Arizona’s climate. Additionally, keeping standard time year-round aligns with daylight hours that better fit outdoor activity and daily life in the hot desert environment. Key points:

• The opt-out occurred around the late 1960s, following broader federal time standards.
• Most of Arizona stays on Mountain Standard Time year-round; the Navajo Nation in the northeastern part of the state does observe DST, creating local exceptions within the state.
• The decision aims to reduce summertime energy use and avoid extending daylight hours into the hottest part of the evening.

If you’d like, I can pull up current official sources or summarize how this interacts with neighboring states and the Navajo Nation.