Time in Arizona, as in all U.S. states, is regulated by the United States Department of Transportation as well as by state and tribal law. All of Arizona is in the Mountain Time Zone. Since 1968, most of the state—with exceptions noted below—does not observe daylight saving time and remains on Mountain Standard Time (MST) all year. This results in most of Arizona having the same time as neighboring California each year from March to November, when locations in the Pacific Time Zone observe daylight saving time.