Time in Arizona, as in all U.S. states, is regulated by the United States Department of Transportationas well as by state and tribal law.
All of Arizona is in the Mountain Time Zone.Since 1968, most of the state—except the Navajo Nation—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.
Unlike most of the United States, Arizona does not observe daylight saving time (DST), with the exception of the Navajo Nation, which does observe DST. The Hopi Reservation, which is not part of the Navajo Nation but is geographically surrounded by it, also does not observe DST. 100 miles (160 km).For this reason, driving the length of Arizona State Route 264 east from Tuba City while DST is in place involves six time zone changes in less than
Because of Arizona's hot climate, DST is largely considered counterproductive. The argument against extending the daylight hours into the evening is that people prefer to do their activities in the cooler morning temperatures. The Navajo Nation, a semi-autonomous Native American territory, follows the United States DST schedule. It lies in northeastern Arizona, northwestern New Mexico, and southeastern Utah and thus maintains the same time throughout tribal lands despite state borders.
On March 21, 1968, the Arizona legislature passed the final version of SB 1, placing Arizona under standard time. : 629 The bill had been working its way through the legislature since January of that year, and was sponsored by state Senators Tenney, Goetze, Porter, Halacy, Garfield, Campbell, Lewis, Gregovich, Giss, Crowley, and Holsclaw. It passed the Senate 25–3–2, and afterwards the bill was passed by the House 49–1–10. It was approved by Governor Jack Williams the same day.
The tz database version 2023c contains two entries for Arizona:
|CC||Coordinates||TZ||Comments||UTC offset||UTC offset DST||Notes|
|US||+332654−1120424||America/Phoenix||MST - AZ (most areas), Creston BC||−07:00||−07:00|
When daylight saving is not active, the time in Phoenix and Albuquerque, New Mexico is the same (Mountain Standard Time), and both are one hour ahead of Los Angeles, California (Pacific Standard Time).
When daylight saving is active, the time in Phoenix (Mountain Standard Time) and Los Angeles (Pacific Daylight Time) is the same, and both are one hour behind Albuquerque (Mountain Daylight Time).
The time in Navajo Nation is always the same as in Albuquerque.
|Los Angeles||Phoenix||Navajo Nation||Albuquerque|
|Standard time (winter)||1 p.m. PST||2 p.m. MST||2 p.m. MST||2 p.m. MST|
|Daylight time (summer)||2 p.m. PDT||2 p.m. MST||3 p.m. MDT||3 p.m. MDT|
A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time.
Daylight saving time (DST), also referred to as daylight savings time, daylight time, or summer time, is the practice of advancing clocks during warmer months so that darkness falls at a later clock time. The typical implementation of DST is to set clocks forward by one hour in either the late winter or spring, and to set clocks back by one hour in the fall to return to standard time. As a result, there is one 23-hour day in early spring and one 25-hour day in the middle of autumn.
The history of standard time in the United States began November 18, 1883, when United States and Canadian railroads instituted standard time in time zones. Before then, time of day was a local matter, and most cities and towns used some form of local solar time, maintained by some well-known clock. The new standard time system was not immediately embraced by all.
The Eastern Time Zone (ET) is a time zone encompassing part or all of 23 states in the eastern part of the United States, parts of eastern Canada, and the state of Quintana Roo in Mexico.
The Mountain Time Zone of North America keeps time by subtracting seven hours from Coordinated Universal Time (UTC) when standard time (UTC−07:00) is in effect, and by subtracting six hours during daylight saving time (UTC−06:00). The clock time in this zone is based on the mean solar time at the 105th meridian west of the Greenwich Observatory. In the United States, the exact specification for the location of time zones and the dividing lines between zones is set forth in the Code of Federal Regulations at 49 CFR 71.
The Pacific Time Zone (PT) is a time zone encompassing parts of western Canada, the western United States, and western Mexico. Places in this zone observe standard time by subtracting eight hours from Coordinated Universal Time (UTC−08:00). During daylight saving time, a time offset of UTC−07:00 is used.
The Hawaii–Aleutian Time Zone observes Hawaii–Aleutian Standard Time (HST) by subtracting ten hours from Coordinated Universal Time (UTC−10:00). The clock time in this zone is based on the mean solar time of the 150th meridian west of the Greenwich Observatory.
In the United States, time is divided into nine standard time zones covering the states, territories and other US possessions, with most of the country observing daylight saving time (DST) for approximately the spring, summer, and fall months. The time zone boundaries and DST observance are regulated by the Department of Transportation, but no single map of those existed until the agency announced intentions to make one in September 2022. Official and highly precise timekeeping services (clocks) are provided by two federal agencies: the National Institute of Standards and Technology (NIST) ; and the United States Naval Observatory (USNO). The clocks run by these services are kept synchronized with each other as well as with those of other international timekeeping organizations.
The Uniform Time Act of 1966, Pub. L. 89–387, 80 Stat. 107, enacted April 13, 1966, was a Law of the United States to "promote the adoption and observance of uniform time within the standard time zones" prescribed by the Standard Time Act of 1918. Its intended effect was to simplify the official pattern of where and when daylight saving time (DST) is applied within the U.S. Prior to this law, each state had its own scheme for when DST would begin and end, and in some cases, which parts of the state should use it.
The Atlantic Time Zone is a geographical region that keeps standard time—called Atlantic Standard Time (AST)—by subtracting four hours from Coordinated Universal Time (UTC), resulting in UTC−04:00. AST is observed in parts of North America and some Caribbean islands. During part of the year, some portions of the zone observe daylight saving time, referred to as Atlantic Daylight Time (ADT), by moving their clocks forward one hour to result in UTC−03:00. The clock time in this zone is based on the mean solar time of the 60th meridian west of the Greenwich Observatory.
UTC−07:00 is an identifier for a time offset from UTC of −07:00. In North America, it is observed in the Mountain Time Zone during standard time, and in the Pacific Time Zone during the other eight months. Some locations use it year-round.
UTC−06:00 is an identifier for a time offset from UTC of −06:00. In North America, it is observed in the Central Time Zone during standard time, and in the Mountain Time Zone during the other eight months. Several Latin American countries and a few other places use it year-round.
Iran Standard Time (IRST) or Iran Time (IT) is the time zone used in Iran. Iran uses a UTC offset UTC+03:30. IRST is defined by the 52.5 degrees east meridian, the same meridian which defines the Iranian calendar and is the official meridian of Iran.
Most of the United States observes daylight saving time, the practice of setting the clock forward by one hour when there is longer daylight during the day, so that evenings have more daylight and mornings have less. Exceptions include Arizona, Hawaii, and the overseas territories of American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the United States Virgin Islands. The Uniform Time Act of 1966 established the system of uniform daylight saving time throughout the US.
Daylight saving time in the Americas is the arrangement in the Americas by which clocks are advanced by one hour in spring and moved back in autumn, to make the most of seasonal daylight. The practice is widespread in North America, with most of Canada and the United States participating, but much less so in Central and South America.
Daylight saving time (DST), also known as summer time, is the practice of advancing clocks during part of the year, typically by one hour around spring and summer, so that daylight ends at a later time of the day. As of 2023, DST is observed in most of Europe, most of North America and parts of Africa and Asia around the Northern Hemisphere summer, and in parts of South America and Oceania around the Southern Hemisphere summer. It was also formerly observed in other areas.
Alaska is officially covered by two time zones - the Alaska Time Zone and the Hawaii-Aleutian Time Zone. The Hawaii-Aleutian Time Zone is used for the Aleutian Islands west of 169°30′W, and the rest of the state uses the Alaska Time Zone. The entirety of Alaska observes daylight saving time.
Time in Maine, as in all US states, is regulated by the United States Department of Transportation. All of Maine is in the Eastern Time Zone (ET) and observes daylight saving time (DST).
Time in Massachusetts, as in all US states, is regulated by the United States Department of Transportation. Massachusetts is in the Eastern Time Zone (ET) and observes daylight saving time (DST).
Permanent standard time refers to the year-round observation of standard time. Likewise, permanent daylight saving time refers to the year-round observation of daylight saving time (DST). Both permanent standard time and permanent DST eliminate the practice of semi-annual clock changes, specifically the advancement of clocks by one hour from standard time to DST in spring and the retraction of clocks by one hour from DST to standard time in fall.
The U.S. Department of Transportation (DOT) oversees the Nation's time zones and the uniform observance of Daylight Saving Time. The oversight of time zones was assigned to DOT because time standards are important for many modes of transportation.