The Alaska Time Zone encompasses almost the entire state of Alaska. Some of the major metropolitan areas under this time zone include Honolulu, Hilo, and Kapaa. The time zone observes Hawaii-Aleutian Standard Time (HAST), which is obtained by subtracting 10 hours from UTC (UTC-10:00). These two areas do not use daylight saving time. The Hawaii-Aleutian Time Zone derives its name from two areas: Hawaii and the Aleutian Islands in Alaska. Time Zones Within the 50 US States Hawaii-Aleutian Time Zone The time zones are defined by their hourly offset from UTC. DST is not observed in the states of Hawaii and Arizona, and some US territories including Puerto Rico, Guam, American Samoa, and the Virgin Islands. Most states observe Daylight Saving Time (DST), which begins at 0200 hours on the second Sunday of March and runs until 0159 hours on the first Sunday of November. The other three time zones are used in US territories: the Atlantic Time Zone is followed in Puerto Rico and the US Virgin Islands the Chamorro Time Zone is followed in Guam and the Samoa Time Zone is followed in American Samoa. However, the 50 states are spread across six standard time zones: Pacific, Central, Mountain, Eastern, Alaska, and Hawaii. United States Time Zonesīy law, time in the United States (US) and its possessions is divided into nine standard time zones. UTC time either changes backward or forward by one hour for every 15 degrees west or east of the prime meridian. The local time in a given time zone is defined by its offset from Coordinated Universal Time (UTC), which is the primary time standard used throughout the world. Time zones are regions on the globe that observe the same standard time. Further advances led to the concept of standard time zones. Apparent and mean solar time may differ by up to 15 minutes. When mechanical clocks became common in the 19th century, mean solar time was used. For example, a sundial was used to estimate the time based on the Sun's apparent position in the sky.
Before the invention of clocks, the time of day was determined by apparent solar time.
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