page_title: Standard time
section_title: North America
hierarchical_section_title: Standard time / History of standard time / North America
caption_attribution_description: Allegheny Observatory The University of Pittsburgh's Allegheny Observatory
context_page_description: Standard time is the synchronization of clocks within a geographical area or region to a single time standard, rather than using solar time or a locally chosen meridian to establish 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 center of the region. Historically, the concept was established during the 19th century to aid weather forecasting and train travel. Applied globally in the 20th century, the geographical areas became extended around evenly spaced meridians into time zones which centered on them. The standard time set in each time zone has come to be defined in terms of offsets from Universal Time. In regions where daylight saving time is used, that time is defined by another offset, from the standard time in its applicable time zones.
  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 replacing the various prime meridians that had previously been used.
context_section_description: Until 1883, each United States railroad chose its own time standards. The Pennsylvania Railroad used the "Allegheny Time" system, an astronomical timekeeping service which had been developed by Samuel Pierpont Langley at the University of Pittsburgh’s Allegheny Observatory (then known as the Western University of Pennsylvania, located in Pittsburgh, Pennsylvania). Instituted in 1869, the Allegheny Observatory's service is believed to have been the first regular and systematic system of time distribution to railroads and cities as well as the origin of the modern standard time system. By 1870 the Allegheny Time service extended over 2,500 miles with 300 telegraph offices receiving time signals.
  However, almost all railroads out of New York ran on New York time, and railroads west from Chicago mostly used Chicago time, but between Chicago and Pittsburgh/Buffalo the norm was Columbus time, even on railroads such as the PFtW&C and LS&MS, which did not run through Columbus. The Santa Fe Railroad used Jefferson City (Missouri) time all the way to its west end at Deming, New Mexico, as did the east–west lines across Texas; Central Pacific and Southern Pacific Railroads used San Francisco time all the way to El Paso. The Northern Pacific Railroad had seven time zones between St. Paul and the 1883 west end of the railroad at Wallula Jct; the Union Pacific Railway was at the other extreme, with only two time zones between Omaha and Ogden.
  In 1870, Charles F. Dowd proposed four time zones based on the meridian through Washington, DC for North American railroads. In 1872. he revised his proposal to base it on the Greenwich meridian. Sandford Fleming, a Scottish-born engineer operating in Canada, proposed worldwide Standard Time at a meeting of the Royal Canadian Institute on February 8, 1879. Cleveland Abbe advocated standard time to better coordinate international weather observations and resultant weather forecasts, which had been coordinated using local solar time. In 1879 he recommended four time zones across the contiguous United States, based upon Greenwich Mean Time. The General Time Convention (renamed the American Railway Association in 1891), an organization of US railroads charged with coordinating schedules and operating standards, became increasingly concerned that if the US government adopted a standard time scheme it would be disadvantageous to its member railroads. William F. Allen, the Convention secretary, argued that North American railroads should adopt a five-zone standard, similar to the one in use today, to avoid government action. On October 11, 1883, the heads of the major railroads met in Chicago at the Grand Pacific Hotel and agreed to adopt Allen's proposed system.
  The members agreed that on Sunday, November 18, 1883, all United States and Canadian railroads would readjust their clocks and watches to reflect the new five-zone system on a telegraph signal from the Allegheny Observatory in Pittsburgh at exactly noon on the 90th meridian. Although most railroads adopted the new system as scheduled, some did so early on October 7 and others late on December 2. The Intercolonial Railway serving the Canadian maritime provinces of New Brunswick and Nova Scotia just east of Maine decided not to adopt Intercolonial Time based on the 60th meridian west of Greenwich, instead adopting Eastern Time, so only four time zones were actually adopted by U.S./Canadian railroads in 1883. Major American observatories, including the Allegheny Observatory, the United States Naval Observatory, the Harvard College Observatory, and the Yale University Observatory, agreed to provide telegraphic time signals at noon Eastern Time.
  Standard time was not enacted into US law until the 1918 Standard Time Act established standard time in time zones; the law also instituted daylight saving time (DST). The daylight saving time portion of the law was repealed in 1919 over a presidential veto, but was reestablished nationally during World War II. In 2007 the US enacted a federal law formalizing the use of Coordinated Universal Time as the basi
caption: Telegraphic equipment used to transmit standard time from the Allegheny Observatory
exif: {"Image Make": "HTC", "Image Model": "PC36100", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image YCbCrPositioning": "Centered", "Image ExifOffset": "122", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "432", "Thumbnail JPEGInterchangeFormatLength": "44894", "EXIF ISOSpeedRatings": "598", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2011:06:30 20:02:12", "EXIF DateTimeDigitized": "2011:06:30 20:02:12", "EXIF ComponentsConfiguration": "YCbCr", "EXIF FocalLength": "123/25", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "1952", "EXIF ExifImageLength": "3264", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "308"}