Time in the United States

Time in the United States, by law, is divided into nine standard time zones covering the states, territories and other US possessions. Most of the U.S. observes daylight saving time for approximately the spring, summer, and fall months. As of August 9, 2007, the standard time zone are defined in terms of hourly offsets from UTC.

About Time in the United States in brief

Summary Time in the United StatesTime in the United States, by law, is divided into nine standard time zones covering the states, territories and other US possessions. Most of the U.S. observes daylight saving time for approximately the spring, summer, and fall months. The time zone boundaries and DST observance are regulated by the Department of Transportation. Official and highly precise timekeeping services are provided by two federal agencies: the National Institute of Standards and Technology and the US Naval Observatory. The clocks run by these services are kept synchronized with each other as well as with those of other international timekeeping organizations. It is the combination of the time zone and daylight saving rules, along with the timekeeping Services, which determines the legal civil time for any U.

S. location at any moment. As of August 9, 2007, the standard time zone are defined in terms of hourly offsets from UTC. For most purposes, UTC is considered interchangeable with GMT, but GMT is no longer precisely defined by the scientific community. In practice, military crews may simply use Zulu time when these islands are on opposite sides of the International Date Line, for example on Thursday, November 21, 2013. Some Outlying Islands are outside the time zones defined by 15 U S. C. §260 and exist in waters defined by nautical time.