This MedLibrary.org supplementary page on Alaska Daylight Time is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
The Alaska Time Zone observes standard time by subtracting nine hours from Coordinated Universal Time (UTC-9). During daylight saving time its time offset is only eight hours (UTC-8). The clock time in this zone is based on the mean solar time of the 135th degree meridian west of the Greenwich Observatory.
The zone includes nearly all of the U.S. state of Alaska and is one hour behind the Pacific Time Zone.
- standard time: Alaska Standard Time (AKST)
- daylight saving: Alaska Daylight Time (AKDT)
The western Aleutians observe Hawaii-Aleutian Time, one hour behind the remainder of the state.
Effective 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.
Contents |
History
The original Alaska time zone was actually known as Alaska-Hawaii Standard Time Zone; that zone is now known as Hawaii-Aleutian Time Zone.
The Alaska Time Zone is the same as what the Yukon Standard Time Zone (YST) was. However, the Yukon Territory switched to the Pacific Standard Time Zone in 1975 and the time zone was not used (except for Yakutat) until 1983 when the state of Alaska decided to move most of the state to UTC-9. Prior to that the Alaska Panhandle communities were on the Pacific Time Zone, while most of the interior was on UTC-10. Nome and the Aleutians previously observed Bering Standard Time or UTC-11.
Anomalies
The Alaska Time Zone is applied to the territory of the state of Alaska to the east of 169°30′ W. Given that the UTC−9 time corresponds to the solar time at 9 × 15° = 135° W (roughly, Juneau), the westernmost locales where Alaska time gets applied are off by 169°30′ − 135° = 34°30′ from their 'physical' time. This means that when a clock correctly set to Alaskan time, at a location just east of 169°30′ W, shows noon, the 'physical' time is actually just 9:42 am. When UTC−8 is applied in the summer, this effect becomes even more apparent, since the solar time at Fresno, California (about 120° W) is used. At a (say) July noon, the physical time at the extreme westerly points of the Alaskan time zone will actually be only 8:42 a.m. Very few people however, notice this 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. In Juneau, solar noon can occur as much as 17 minutes before "noon" clock time.
In Anchorage, visitors from more southerly latitudes are often surprised to see the sun set at 11:41 pm on the summer solstice, but the actual 'physical time' is 9:41 pm. This is because at 150° W, Anchorage is a full solar hour behind the legal time zone and observes daylight saving time as well. Some local residents refer to this phenomenon as "double daylight time". In Fairbanks, the same circumstances cause sunset to occur at 12:47 am on the next calendar day. In the winter, even without daylight saving time, another anomaly is that on the winter solstice in Nome, the sunrise is actually after "noon" clock time, at 12:02 pm lasting for about 3 hours before sunset.
Major Metropolitan Areas
See also
Sources
Wikipedia content modification information:
- This page was last modified on 30 August 2008, at 14:33.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Alaska Daylight Time".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.