Alaska Daylight Time
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The Alaska Time Zone observes
standard time Standard time is the synchronisation of clocks within a geographical region to a single time standard, rather than a local mean time standard. Generally, standard time agrees with the local mean time at some meridian that passes through the r ...
by subtracting nine hours from
Coordinated Universal Time Coordinated Universal Time or UTC is the primary time standard by which the world regulates clocks and time. It is within about one second of mean solar time (such as UT1) at 0° longitude (at the IERS Reference Meridian as the currently used ...
( UTC−09:00). During
daylight saving time Daylight saving time (DST), also referred to as daylight savings time or simply daylight time (United States, Canada, and Australia), and summer time (United Kingdom, European Union, and others), is the practice of advancing clocks (typicall ...
its
time offset The UTC offset is the difference in hours and minutes between Coordinated Universal Time (UTC) and local solar time, at a particular place. This difference is expressed with respect to UTC and is generally shown in the format , , or . So if the tim ...
is eight hours ( UTC−08:00). The clock time in this zone is based on
mean solar time Solar time is a calculation of the passage of time based on the position of the Sun in the sky. The fundamental unit of solar time is the day, based on the synodic rotation period. Two types of solar time are apparent solar time (sundial ti ...
at the
135th meridian west The meridian 135° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, North America, the Pacific Ocean, the Southern Ocean, and Antarctica to the South Pole. The 135th meridian west forms a grea ...
of the
Greenwich Observatory The Royal Observatory, Greenwich (ROG; known as the Old Royal Observatory from 1957 to 1998, when the working Royal Greenwich Observatory, RGO, temporarily moved south from Greenwich to Herstmonceux) is an observatory situated on a hill in G ...
. The zone includes nearly all of the U.S. state of
Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
and is one hour behind the
Pacific Time Zone 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) ...
. *standard time: Alaska Standard Time (AKST) *daylight saving time: Alaska Daylight Time (AKDT) The western
Aleutian Islands The Aleutian Islands (; ; ale, Unangam Tanangin,”Land of the Aleuts", possibly from Chukchi language, Chukchi ''aliat'', "island"), also called the Aleut Islands or Aleutic Islands and known before 1867 as the Catherine Archipelago, are a cha ...
observe Hawaii–Aleutian Time, one hour behind the remainder of the state. The largest city in the Alaskan Time Zone is
Anchorage, Alaska Anchorage () is the largest city in the U.S. state of Alaska by population. With a population of 291,247 in 2020, it contains nearly 40% of the state's population. The Anchorage metropolitan area, which includes Anchorage and the neighboring Ma ...
. The
Anchorage Metropolitan Area The Anchorage Metropolitan Statistical Area, as defined by the United States Census Bureau, is an area consisting of the Municipality of Anchorage and the Matanuska-Susitna Borough in the south central region of Alaska. As of the 2010 census, ...
is the largest metropolitan area in the zone. Effective from 2007, the local time changes from AKST to AKDT at 02:00 LST to 03:00 LDT on the second Sunday in March and returns at 02:00 LDT to 01:00 LST on the first Sunday in November.


History

Two time zones have been referred to as the "Alaska Time Zone": a zone based on UTC−10:00 that covered much of Central Alaska in the early 20th century, and a zone based on UTC−09:00 zone that has covered all of the state except the Aleutian Islands since 1983. The
Standard Time Act The Standard Time Act of 1918, also known as the Calder Act, was the first United States federal law implementing Standard time and Daylight saving time in the United States. It defined five time zones for the United States and authorized the ...
of 1918 authorized the
Interstate Commerce Commission The Interstate Commerce Commission (ICC) was a regulatory agency in the United States created by the Interstate Commerce Act of 1887. The agency's original purpose was to regulate railroads (and later trucking) to ensure fair rates, to eliminat ...
to define each time zone. The United States Standard Alaska Time was designated as UTC−10:00. Some references prior to 1967 refer to this zone as Central Alaska Standard Time (CAT) or as Alaska Standard Time (AST). In 1966, the
Uniform Time Act The Uniform Time Act of 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 ...
renamed the UTC−10:00 zone to Alaska-Hawaii Standard Time (AHST), effective April 1, 1967. This zone was renamed in 1983 to Hawaii-Aleutian Standard Time when the majority of Alaska was moved out of the zone. Prior to 1983, the current Alaska Time Zone (UTC−09:00) was known as the
Yukon Time Zone 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.UTC-based calculations began in 1972. Before that they w ...
, observing Yukon Standard Time (YST). This time zone included Canada's
Yukon Territory Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...
and a small portion of Alaska including Yakutat. The
Alaska Panhandle Southeast Alaska, colloquially referred to as the Alaska(n) Panhandle, is the southeastern portion of the U.S. state of Alaska, bordered to the east and north by the northern half of the Canadian province of British Columbia (and a small part ...
communities were in the
Pacific Time Zone 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) ...
, while most of the interior was on UTC−10:00. Nome and the Aleutians previously observed
Bering Standard Time Bering may refer to: * Vitus Bering (1681–1741), Danish-born navigator in the service of the Russian Navy * Maritime features of Alaska/Siberia region: ** Bering Sea, body of water in the North Pacific Ocean ** Bering Strait, sea strait between ...
or UTC−11:00. In 1975, the Yukon Territory switched to Pacific Standard Time, leaving Yakutat the only land area in the zone. With the reorganization of Alaska's time zones in 1983 to place the entire state in either a zone based on UTC−09:00 or UTC−10:00, the Yukon Time Zone based on UTC−09:00 was renamed the Alaska Time Zone.


Anomalies

The Alaska Time Zone applies to the territory of the state of
Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
east of 169°30′ W, that is, the entire state minus the westernmost portions of the Aleutian Islands. Solar time zones are 15° wide. UTC−09:00 time corresponds to the solar time at 9 × 15° = 135° W (roughly,
Juneau The City and Borough of Juneau, more commonly known simply as Juneau ( ; tli, Dzánti K'ihéeni ), is the capital city of the state of Alaska. Located in the Gastineau Channel and the Alaskan panhandle, it is a unified municipality and the se ...
, which is in the southeast panhandle). Thus, the westernmost locales of the Alaska Time Zone are off by up to 169°30′ − 135° = 34°30′ from local solar time, or slightly more than 2 hours and 17 minutes. At noon Alaskan Time at a location just east of 169°30′ W, local solar time is only about 9:42 a.m. The sun will not reach culmination for another 2 hours and 18 minutes. When UTC−08:00 is applied in the summer (because of
daylight saving time Daylight saving time (DST), also referred to as daylight savings time or simply daylight time (United States, Canada, and Australia), and summer time (United Kingdom, European Union, and others), is the practice of advancing clocks (typicall ...
), this effect becomes even more apparent. For example, on June 12 at noon AKDT, the
solar time Solar time is a calculation of the passage of time based on the position of the Sun in the sky. The fundamental unit of solar time is the day, based on the synodic rotation period. Two types of solar time are apparent solar time (sundial ti ...
at the extreme westerly points of the Alaskan time zone will be only 8:42 a.m., nearly 3 hours and 18 minutes behind clock time. Very few people notice this, however, as these locations are virtually uninhabited, and for the very few people who do live there, the long days in the summer and short days in the winter make the sunrise and sunset times less important than areas closer to the equator. By contrast, in Juneau, which is much closer to the 135° west meridian, mean
solar noon Noon (or midday) is 12 o'clock in the daytime. It is written as 12 noon, 12:00 m. (for meridiem, literally 12:00 noon), 12 p.m. (for post meridiem, literally "after noon"), 12 pm, or 12:00 (using a 24-hour clock) or 1200 (military time). Solar ...
occurs around 11:57 a.m., very close to noon on the clock. In
Anchorage Anchorage () is the largest city in the U.S. state of Alaska by population. With a population of 291,247 in 2020, it contains nearly 40% of the state's population. The Anchorage metropolitan area, which includes Anchorage and the neighboring Ma ...
, visitors from more southerly latitudes are often surprised to see the sun set at 11:41 p.m. on the summer
solstice A solstice is an event that occurs when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around June 21 and December 21. In many countr ...
while the solar time is 9:41 p.m. Anchorage is at 150° W, one hour further west from the solar time for UTC−09:00. Thus, Anchorage is one solar hour behind the legal time zone and observes daylight saving time as well for a two-hour discrepancy between legal time and solar time. Some local residents refer to this phenomenon as "double daylight time". In
Fairbanks Fairbanks is a home rule city and the borough seat of the Fairbanks North Star Borough in the U.S. state of Alaska. Fairbanks is the largest city in the Interior region of Alaska and the second largest in the state. The 2020 Census put the po ...
, the same circumstances cause sunset to occur at 12:47 a.m. the next calendar day and the solar sunset is at 10:47 p.m. Even without daylight saving time, another anomaly is that on the winter solstice in Nome, the sunrise is after "noon" clock time, at 12:02 p.m., about 4 hours before sunset at 3:56 p.m. The territory of the state of Alaska spans almost as much longitude as the contiguous United States (57.5° vs. 57.6°) so the use of two time zones will inevitably lead to some distortions. Alaska would naturally fall into five time zones, with the greatest territory more correctly in UTC−10:00 and UTC−11:00, with Adak more correctly in UTC–12:00 and
Cape Wrangell Cape Wrangell is considered to be the westernmost point of Alaska and all of the United States by direction of travel, named after the Russian explorer and seaman Ferdinand von Wrangel. It is located on Attu Island, which is situated in the Near ...
in UTC–13:00 as sunset can be late as
midnight Midnight is the transition time from one day to the next – the moment when the date changes, on the local official clock time for any particular jurisdiction. By clock time, midnight is the opposite of noon, differing from it by 12 hours. ...
. But political and logistical considerations have led to the use of two time zones, leading to the distortions mentioned above.


Cities

*
Anchorage, Alaska Anchorage () is the largest city in the U.S. state of Alaska by population. With a population of 291,247 in 2020, it contains nearly 40% of the state's population. The Anchorage metropolitan area, which includes Anchorage and the neighboring Ma ...
*
Fairbanks, Alaska Fairbanks is a home rule city and the borough seat of the Fairbanks North Star Borough in the U.S. state of Alaska. Fairbanks is the largest city in the Interior region of Alaska and the second largest in the state. The 2020 Census put the po ...
*
Juneau, Alaska The City and Borough of Juneau, more commonly known simply as Juneau ( ; tli, Dzánti K'ihéeni ), is the capital city of the state of Alaska. Located in the Gastineau Channel and the Alaskan panhandle, it is a unified municipality and the se ...


See also

*
Time in Alaska 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 a ...
*
Time zone A time zone is an area which observes a uniform standard time for legal, Commerce, commercial and social purposes. Time zones tend to follow the boundaries between Country, countries and their Administrative division, subdivisions instead of ...
*
Effects of time zones on North American broadcasting The scheduling of television programming in North America (namely the United States, Canada, and Mexico) must cope with different time zones. The United States (excluding territories) has six time zones ( Hawaii–Aleutian, Alaska, Pacific, Mou ...


References


Sources


The official U.S. time for the Alaska Time Zone
{{North American time zones Time zones Geography of Alaska Time zones in the United States