Hawaii–Aleutian Time Zone Hawaii–Aleutian Time Zone The Hawaii–Aleutian Time Zone observes Hawaii–Aleutian Standard Time (HST), by subtracting ten hours from Coordinated Universal Time (). The clock time in this zone is based on the mean solar time of the 150th meridian west of the Greenwich Observatory. 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 (HDT, ), while Hawaii stays on standard time. From 1900 until 1947, GMT−10:30 was used as standard time in Hawaii. French
Aleutian Arc Aleutian Arc The Aleutian Arc is a large volcanic arc in the U.S. state of Alaska. It consists of a number of active and dormant volcanoes that have formed as a result of subduction along the Aleutian Trench. Although taking its name from the Aleutian Islands, this term is a geologic grouping rather than a geographic one, and the Aleutian Arc extends through the Alaska Peninsula following the Aleutian Range to the Aleutian Islands. The Aleutian Arc reflects subduction of the Pacific Plate beneath the North American Plate. It extends from the Kamchatka Peninsula in the west to the Gulf