Why don't Arizona and Hawaii participate in Daylight Saving Time?

Arizona

When Congress passed the Uniform Time Act in 1966, Arizona tried observing daylight savings for a year and decided to not observe it after much negative reaction. They have never observed daylight savings since.

During daylight saving time (spring through fall), Arizona is on Pacific time. All other months of the year they observe Mountain time. The only exception in Arizona is the Navajo Nation, in northeastern Arizona, which does observe Daylight Saving Time.

Hawaii

Hawaii is closer to the equator and experiences much less variance in daylight than the rest of the country and therefore opts out of observing Daylight Saving Time.