Everyday Life
Time Zones
Updated 2025-11-02
Definition
Geographic regions observing a common standard time, typically offset from Coordinated Universal Time (UTC) by whole or half-hour increments. The world is divided into 38 active time zones. The continental United States uses four primary zones, Eastern (UTC−5), Central (UTC−6), Mountain (UTC−7), and Pacific (UTC−8), with Alaska, Hawaii, and U.S. territories adding five more. Most of the U.S. observes daylight saving time from the second Sunday in March to the first Sunday in November, advancing clocks one hour. Arizona, Hawaii, and U.S. territories do not.
Primary source: NIST official U.S. time
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