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),[1] and the rest of the state uses the Alaska Time Zone.[2] 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 (DST) like its neighbor Stewart, British Columbia, with the exception of the U.S. Post Office (because it is a federal facility).[3] [4] [5]
As part of Russian America, Alaska used the Julian calendar and followed the same day of the week as Asia, using the date of the eastern hemisphere. In 1867, Alaska became a United States territory (through the Alaska Purchase) and began using the Gregorian calendar, aligning with the same day of the week as the Americas, using the date of the western hemisphere. The switch was achieved by repeating the same day of the week and skipping eleven days of the month instead of twelve during the 19th century, so that the purchase date of Friday, October 6 (Julian) was followed once again by Friday, October 18 (instead of Saturday, October 19 in Gregorian).[6] That change redrew the International Date Line from being east to west of the territory to realign itself from Asian to American dates, thus shifting it from the date of the eastern hemisphere to the western hemisphere.
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.[7]
In 1900, "Alaska Standard Time" was established within the state as .[8]
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 .[9]
On January 20, 1942, all of the United States, including Alaska, began to observe War Time.[10] Standard time in the United States advanced by one hour and would remain so until September 25, 1945, when the act was repealed.[11]
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.[12] The Uniform Time Act also defined four time zones that Alaska would use:[13]
In April 1983, the Alaska Legislature approved a resolution asking the Department of Transportation to switch Alaska to use only two time zones.[19] It was approved by Secretary of Transportation Elizabeth Dole on September 15, 1983, and took effect on October 30, 1983.[20] [21] Areas east of Unalaska began using the Yukon Time Zone . Most of the Aleutian Islands, previously on Bering Time, were now using Alaska–Hawaii Time.[22] As an act of Congress was required to change the name of the time zones,[23] the time zones did not gain their modern names (Alaska Time and Hawaii–Aleutian Time) until November 30, 1984.[24]
| Period in use | Time offset from GMT/UTC | Name of time |
|---|---|---|
| Wednesday, July 15, 1741 – Friday, October 6, 1867 | GMT+14:59 (in Sitka) | Local Mean Time |
| GMT+12:24 (in Aleutian Islands) | ||
| Friday, October 18, 1867 – 1900 | GMT−09:01 (in Sitka) | Local Mean Time |
| GMT−11:36 (in Aleutian Islands) | ||
| 1900 – 1918 | GMT−09:00 (including Aleutian Islands) | Alaska Standard Time |
| 1918 – January 19, 1942 | GMT−08:00 (Panhandle Areas) | Pacific Standard Time |
| GMT−09:00 (in Yakutat) | Yukon Standard Time | |
| GMT−10:00 | Alaska Standard Time | |
| GMT−11:00 (Nome, and Aleutian Islands) | Bering Standard Time | |
| January 20, 1942 – September 30, 1945 | GMT−07:00 (Panhandle Areas) | Pacific War Time |
| GMT−08:00 (in Yakutat) | Yukon War Time | |
| GMT−09:00 | Alaska War Time | |
| GMT−10:00 (Nome, and Aleutian Islands) | Bering War Time | |
| September 30, 1945 – March 31, 1967 | GMT−08:00 (Panhandle Areas) | Pacific Standard Time |
| GMT−09:00 (in Yakutat) | Yukon Standard Time | |
| GMT−10:00 | Alaska Standard Time | |
| GMT−11:00 (Nome, and Aleutian Islands) | Bering Standard Time | |
| April 1, 1967 – October 30, 1983 | GMT/UTC−08:00 (Panhandle Areas) | Pacific Standard Time |
| GMT/UTC−09:00 (in Yakutat) | Yukon Standard Time | |
| GMT/UTC−10:00 | Alaska–Hawaii Standard Time | |
| GMT/UTC−11:00 (Nome, and Aleutian Islands) | Bering Standard Time | |
| October 30, 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 | Alaska Daylight Time |
The tz database version contains seven time zones for Alaska for historical reasons. Only three (America/Adak, America/Anchorage, and America/Metlakatla) are currently in use.