Standard time is the result of synchronizing clocks in different geographical locations within a time zone to the same time rather than using the local meridian as in local mean time or solar time. Historically, this helped in the process of weather forecasting and train travel. The concept became established in the late 19th century. The time so set has come to be defined in terms of offsets from Universal Time. Where daylight saving time is used, the term standard time typically refers to the time without daylight saving time.
The adoption of Standard Time, because of the inseparable correspondence between time and longitude, solidified the concepts of halving the globe into an eastern and western hemisphere, with one Prime Meridian (as well its opposite International Dateline) replacing the various Prime Meridians that were in use.
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A standardized time system was first used by British railways on December 11, 1847, when they switched from local mean time to Greenwich Mean Time (GMT). It was also given the name Railway time reflecting the important role the railway companies played in bringing it about. The vast majority of Great Britain's public clocks were being synchronised using GMT by 1855.
Prior to 1883, local mean time was used throughout North America, resulting in an inordinate number of local times. This caused convoluted regional and national train schedules. In 1870, Charles F. Dowd proposed four time zones based on the meridian through Washington, DC for for North American railroads.[1] In 1872, he recommended the Greenwich meridian. Sandford Fleming, a Canadian, proposed worldwide Standard Time at a meeting of the Royal Canadian Institute on February 8, 1879. Cleveland Abbe advocated for standard time in order to more effectively coordinate international weather observations and resultant weather forecasts, which had previously been coordinated using local solar time. He recommended the concept of four time zones across the contiguous United States, based upon Greenwich Mean Time, in 1879.[2] On October 11, 1883, the heads of the major railroads met in Chicago at the former Grand Pacific Hotel[3] to adopt their own Standard Time System of five standard time zones for the continental U.S.A. and Canada. The new system was adopted by most states within one year after railroads did so. At noon on November 18, 1883, the U.S. Naval Observatory changed its telegraphic signals to correspond to the change. The Standard Time Act of 1918 established standard time in time zones in U.S. law as well as daylight saving time (DST). The daylight savings time law was repealed in 1919 over a presidential veto, but reestablished nationally during World War II.[4][5]
In 2007 the United States enacted a federal law formalizing the use of Coordinated Universal Time as the basis of standard time, and the role of the Secretary of Commerce (effectively, the National Institute of Standards and Technology) and the Secretary of the Navy (effectively, the U.S. Naval Observatory) in interpreting standard time.[6]