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  2. History of time in the United States - Wikipedia

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

    The evolution of United States standard time zone boundaries from 1919 to 2024 in five-year increments. Plaque in Chicago marking the creation of the four time zones of the continental US in 1883 Colorized 1913 time zone map of the United States, showing boundaries very different from today Map of U.S. time zones during between April 2, 2006, and March 11, 2007.

  3. 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.

  4. 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 ...

  5. 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 ...

  6. 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 ...

  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. Standard Time Act - Wikipedia

    en.wikipedia.org/wiki/Standard_Time_Act

    Passed the House on March 15, 1918 (253-40) Signed into law by President Woodrow Wilson on March 19, 1918. The Standard Time Act of 1918, also known as the Calder Act, was the first United States federal law implementing Standard time and Daylight saving time in the United States. [2] It defined five time zones for the continental United States ...

  9. Sandford Fleming - Wikipedia

    en.wikipedia.org/wiki/Sandford_Fleming

    Inventing, most notably standard time. Sir Sandford Fleming FRSC KCMG (January 7, 1827 – July 22, 1915) was a Scottish Canadian engineer and inventor. Born and raised in Scotland, he emigrated to colonial Canada at the age of 18. He promoted worldwide standard time zones, a prime meridian, and use of the 24-hour clock as key elements to ...