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  2. Time zone - Wikipedia

    en.wikipedia.org/wiki/Time_zone

    Time zones of the world. A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time.

  3. History of time in the United States - Wikipedia

    en.wikipedia.org/wiki/History_of_time_in_the...

    The history of standard time in the United States began November 18, 1883, when United States and Canadian railroads instituted standard time in time zones. Before then, time of day was a local matter, and most cities and towns used some form of local solar time, maintained by some well-known clock (for example, on a church steeple or in a ...

  4. Standard time - Wikipedia

    en.wikipedia.org/wiki/Standard_time

    Standard time is the synchronization of clocks within a geographical region to a single time standard, rather than a local mean time standard. Generally, standard time agrees with the local mean time at some meridian that passes through the region, often near the centre of the region. Historically, standard time was established during the 19th ...

  5. International Meridian Conference - Wikipedia

    en.wikipedia.org/wiki/International_Meridian...

    The International Meridian Conference was a conference held in October 1884 in Washington, D.C., in the United States, to determine a prime meridian for international use. [1] The conference was held at the request of U.S. President Chester A. Arthur. [1] The subject to discuss was the choice of "a meridian to be employed as a common zero of ...

  6. Time in the United States - Wikipedia

    en.wikipedia.org/wiki/Time_in_the_United_States

    Time in the United States. In the United States, time is divided into nine standard time zones covering the states, territories and other US possessions, with most of the country observing daylight saving time (DST) for approximately the spring, summer, and fall months. The time zone boundaries and DST observance are regulated by the Department ...

  7. Universal Time - Wikipedia

    en.wikipedia.org/wiki/Universal_Time

    Universal Time. Universal Time (UT or UT1) is a time standard based on Earth's rotation. [1] While originally it was mean solar time at 0° longitude, precise measurements of the Sun are difficult. Therefore, UT1 is computed from a measure of the Earth's angle with respect to the International Celestial Reference Frame (ICRF), called the Earth ...

  8. Coordinated Universal Time - Wikipedia

    en.wikipedia.org/wiki/Coordinated_Universal_Time

    Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communication, navigation, scientific research, and commerce. UTC has been widely embraced by most countries and ...

  9. International Date Line - Wikipedia

    en.wikipedia.org/wiki/International_Date_Line

    The International Date Line (IDL) is the line between the South and North Poles that is the boundary between one calendar day and the next. It passes through the Pacific Ocean, roughly following the 180.0° line of longitude and deviating to pass around some territories and island groups. Crossing the date line eastbound decreases the date by ...