In 1870 Charles F. Dowd had proposed four time zones based on the meridian through Washington, DC for North American railroads. 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 standard time to better coordinate international weather observations and resultant weather forecasts, which had been coordinated using local solar time. He recommended four time zones across the contiguous United States, based upon Greenwich Mean Time, in 1879. The General Time Convention (renamed the American Railway Association in 1891), an organization of American railroads aimed at coordinating schedules and operating standards, became increasingly concerned that if the United States government adopted a standard time scheme it would work to the disadvantage of its member railroads. William F. Allen, the secretary of the General Time Convention, 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 former 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 sent 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 provided telegraphic time signals at noon Eastern Time.

en.wikipedia.org/wiki/Standard_time