Starting this upcoming Sunday, March 14 at 2 a.m., approximately 70 million countries will move their clocks forward in observation of daylight saving time.
Arizona does not set the clocks forward an hour for DST, with the exception of the Navajo Nation, who set the clock forward one hour to Mountain Daylight Time. Instead, Phoenix and most of Arizona observe Mountain Standard Time.
Arizona exempted itself from observing DST in 1968, according to the Congressional Research Service.
DST is "largely unncessary" due to Arizona's hot climate and that the argument against extending the daylight hours is that people prefer to do their activities in cooler evening temperatures.
The only other state that does not observe daylight saving time is Hawaii, which exempted itself in 1967.