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 (Islands of Four Mountains, Andreanof Islands, Rat Islands and Near Islands),and the rest of the state uses the Alaska Time Zone. The entirety of Alaska observes daylight saving time.
The town of Hyder, because it essentially is a single town split by the border between the United States and Canada, unofficially observes Pacific Time including DST (UTC−08:00, DST UTC−07:00) like its neighbor Stewart, British Columbia, with the exception of the U.S. Post Office (because it is a federal facility).
As part of Russian America, Alaska used the Julian calendar and the same day of the week as Asia. In 1867, Alaska became a United States territory (through the Alaska Purchase) and began using the Gregorian calendar and the same day of the week as the Americas. The switch was achieved by repeating the same day of the week and skipping eleven days of the month, so that the purchase date of Friday, October 6 (Julian) was followed by Friday, October 18 (Gregorian).
Before time zones were introduced, every place used local observation of the sun to set its clocks, which meant that every location used a different local mean time based on its longitude. For example, Sitka, the capital of Alaska at the time, at longitude 135°20′W, had a local time equivalent to UTC+14:59 under Russia and UTC−09:01 under the United States.
In 1900, "Alaska Standard Time" was established within the state as UTC−09:00.
In 1918, the United States Congress passed the Standard Time Act, which defined a standard time zone for Alaska - United States Standard Alaska Time, set at UTC−10:00.
On January 20, 1942, all of the United States, including Alaska, began to observe War Time.Standard time in the United States advanced by one hour and would remain so until September 25, 1945, when the act was repealed.
In 1966, Congress passed the Uniform Time Act. The Uniform Time Act introduced Daylight Saving Time uniformly in the United States, which Alaska would begin observing on April 28, 1968.The Uniform Time Act also defined four time zones that Alaska would use:
In April 1983, the Alaska Legislature approved a resolution asking the Department of Transportation to switch Alaska to use only two time zones.It was approved by Secretary of Transportation Elizabeth Dole on September 15, 1983, and took effect on October 30, 1983. Areas east of Unalaska began using the Yukon Time Zone (UTC−09:00). Most of the Aleutian Islands, previously on Bering Time, were now using Alaska-Hawaii Time. As an act of Congress was required to change the name of the time zones, the time zones did not gain their modern names (Alaska Time and Hawaii-Aleutian Time) until November 30, 1984.
|Period in use||Time offset from UTC||Name of time|
|Wednesday, July 15, 1741 – Friday, October 6, 1867 (Julian Calendar)||UTC+14:59 (in Sitka)||Local Mean Time|
|UTC+12:24 (in Aleutian Islands)|
|Friday, October 18, 1867 – 1900 (Gregorian Calendar)||UTC−09:01 (in Sitka)||Local Mean Time|
|UTC−11:36 (in Aleutian Islands)|
|1900 – 1918||UTC−09:00 (including Aleutian Islands)||Alaska Standard Time|
|1918 – March 31, 1967||UTC−08:00 (Panhandle Areas)||Pacific Standard Time|
|UTC−09:00 (in Yakutat)||Yukon Standard Time|
|UTC−10:00||Alaska Standard Time|
|UTC−11:00 (Nome, and Aleutian Islands)||Bering Standard Time|
|April 1, 1967 – 1983||UTC−08:00 (Panhandle Areas)||Pacific Standard Time|
|UTC−09:00 (in Yakutat)||Yukon Standard Time|
|UTC−10:00||Alaska–Hawaii Standard Time|
|UTC−11:00 (Nome, and Aleutian Islands)||Bering Standard Time|
|1983 – Present||UTC−09:00 (in Juneau)||Alaska Time Zone|
|UTC−10:00 (in Aleutian Islands)||Hawaii-Aleutian Time Zone|
|2007 − Present||UTC−08:00 (except in Aleutian Islands)||Alaska Daylight Time|
The tz database version 2023c contains seven time zones for Alaska for historical reasons. Only three (America/Adak, America/Anchorage, and America/Metlakatla) are currently in use.
|CC||Coordinates||TZ||Comments||UTC offset||UTC offset DST||Notes|
|US||+611305−1495401||America/Anchorage||Alaska (most areas)||−09:00||−08:00|
|US||+581807−1342511||America/Juneau||Alaska - Juneau area||−09:00||−08:00|
|US||+571035−1351807||America/Sitka||Alaska - Sitka area||−09:00||−08:00|
|US||+593249−1394338||America/Yakutat||Alaska - Yakutat||−09:00||−08:00|
|US||+515248−1763929||America/Adak||Alaska - western Aleutians||−10:00||−09:00|
|US||+550737−1313435||America/Metlakatla||Alaska - Annette Island||−09:00||−08:00|
Western European Summer Time is a summer daylight saving time scheme, 1 hour ahead of Greenwich Mean Time and Coordinated Universal Time. It is used in:
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 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 Alaska Time Zone observes standard time by subtracting nine hours from Coordinated Universal Time (UTC−09:00). During daylight saving time its time offset is eight hours (UTC−08:00). The clock time in this zone is based on mean solar time at the 135th meridian west of the Greenwich Observatory.
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.
Central European Time (CET) is a standard time of Central, and parts of Western Europe, which is one hour ahead of Coordinated Universal Time (UTC). The time offset from UTC can be written as UTC+01:00. It is used in most parts of Europe and in a few North African countries. CET is also known as Middle European Time and by colloquial names such as Amsterdam Time, Berlin Time, Brussels Time, Budapest Time,Madrid Time, Paris Time, Rome Time,Prague time,Warsaw Time or Romance Standard Time (RST).
Western European Time is a time zone covering parts of western Europe and consists of countries using UTC±00:00. It is one of the three standard time zones in the European Union along with Central European Time and Eastern European Time.
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.
Central European Summer Time, sometimes referred to as Central European Daylight Time (CEDT), is the standard clock time observed during the period of summer daylight-saving in those European countries which observe Central European Time during the other part of the year. It corresponds to UTC+02:00, which makes it the same as Eastern European Time, Central Africa Time, South African Standard Time, Egypt Standard Time and Kaliningrad Time in Russia.
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.
The Yukon Time Zone was a time zone that kept standard time; Yukon Standard Time (YST) was obtained by subtracting nine hours from Coordinated Universal Time (UTC) resulting in UTC−09:00. Yukon Daylight Time (YDT) when observed was eight hours behind UTC. In 1983 the UTC−09:00 based time zone was restructured, and it was renamed the Alaska Time Zone in 1984.
UTC−11:00 is an identifier for a time offset from UTC of −11:00. This time is used in Niue, American Samoa, Swains Island, and parts of the United States Minor Outlying Islands. This is the latest inhabited time zone, meaning this is the last inhabited time zone to celebrate the New Year, as the world's latest time zone (UTC-12:00) is completely uninhabited.
UTC−09:00 is an identifier for a time offset from UTC of −09:00. This time is used in:
UTC−08:00 is an identifier for a time offset from UTC of −08:00. This time is used:
Australia uses three main time zones: Australian Eastern Standard Time, Australian Central Standard Time and Australian Western Standard Time.
Canada is divided into six time zones. Most areas of the country's provinces and territories operate on standard time from the first Sunday in November to the second Sunday in March and daylight saving time the rest of the year.
The Chamorro Time Zone, formerly the Guam Time Zone, is a United States time zone which observes standard time ten hours ahead of Coordinated Universal Time (UTC+10:00). The clock time in this zone is based on the mean solar time of the 150th meridian east of the Greenwich Observatory.
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 (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.
Alaskans will advance their clocks one hour next Sunday as the state for the first time observes Daylight Savings Time.
The big change was in Juneau, Ketchikan and Sitka, the major towns in southeast Alaska, where clocks shifted back two hours to Yukon time. After decades on Pacific time, this region will now be an hour earlier, as will Anchorage and Fairbanks, which formerly were two hours earlier than Pacific time.