HAST UTC−10:00 DST began 12 Mar 2017 | HADT UTC−9:00 DST ends 5 Nov 2017 | |
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HADT 10:01 pm on 17 Mar 2017 HAST 9:01 pm on 17 Mar 2017 | ||
The Hawaii–Aleutian Time Zone observes Hawaii–Aleutian Standard Time (HAST), 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.
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The zone takes its name from the two areas it includes: Hawaii and the portion of Alaska's Aleutian Islands west of 169° 30′ W longitude.
During daylight saving time, the Alaskan portion observes Hawaii–Aleutian Daylight Time (HADT, UTC−9), while Hawaii stays on standard time.
From 1900 until 1947, GMT−10:30 was used as standard time in Hawaii.
French Polynesia uses UTC−10 for its major cities. The Cook Islands also use the same time. These areas do not use DST. "Hawaii–Aleutian Time Zone" is a U.S. term and for that reason the Polynesian areas are not considered to be a part of the Hawaii–Aleutian Time Zone.