On November 18, 1883, precisely at noon, North American railroads switched to a new standard time system for rail operations, which they called Standard Railway Time(SRT). Almost immediately after being implemented, many American cities enacted ordinances, thus resulting in the creation of time “zones.” The four standard time zones adopted were Eastern, Central, Mountain, and Pacific. Though tailored to the railroad companies’ train schedules, the new system was quickly adopted nationwide, forestalling federal intervention in civil time for more than thirty years, until 1918, when daylight saving time was introduced.

Before clocks, people marked time by the sun and the phases of the moon. With the development of the railway and the invention of the telegraph, accurate time became more important. Prior to adopting SRT, trains traveling east or west between towns had a difficult time maintaining coherent schedules and smooth operations. The new time zones were each one-hour wide, simplifying train schedules and virtually everything else in increasingly industrialized America.

The SRT system was based on geography, economics, the locations of major cities, and the habits and needs of the populace. The one-hour difference in zones was a result of the fact that fifteen degrees of longitude corresponds to one-hour difference in solar time. It was decided that official time would correspond to the mean solar time of the closest meridian of longitude that could be divided evenly by fifteen degrees and was referenced to the meridian at Greenwich, England. There are twenty-four meridians fifteen degrees apart that circle the globe, beginning with Greenwich, the “prime” meridian.

Impetus for the adoption of standardized time, however, did not originate with the railroads. Astronomers and geophysicists, trying to get simultaneous observations from scattered geographical locations, had long advocated standardized time.

Beginning in 1875, Cleveland Abbe—astronomer, meteorologist, and the first head of the U.S. Weather Bureau—lobbied the American Meteorological Society (AMS) to take action on a uniform standard time. The AMS then established the Committee on Standard Time and named Abbe chairman. In 1879, the committee’s Report on Standard Time, the key document leading to the implementation of standard time in the U.S., was released. In 1881, the railroad industry’s General Time Convention (GTC), a group of officials involved in scheduling, took up the proposal for standardizing time and in 1883, convinced by the AMS report, decided to adopt SRT. The following year, a conference in Washington took up the proposal for international implementation.

The goals of the 1884 International Meridian ConferenceExternal, were to agree on a common initial meridian (in consideration of the longstanding preference for the Greenwich meridian) and ultimately to standardize time worldwide. A globally recognized initial (prime) meridian had to be established because, unlike latitude, there is no obvious starting point for the meridian lines around the globe that specify east-west positions of longitude, and thus one had to be designated and agreed upon. Greenwich, England, site of the Royal Observatory, was already widely used by mariners, mapmakers, and navigators, and was the prime candidate. Its selection by the railroads also forestalled potential conflict between U.S. cities vying for the honor. International time zones were established according to the SRT system that was implemented in 1893, creating Universal Time (UT) based on the Greenwich meridian, which became “time zero.” The twenty-four standard meridians marked the centers of the zones around the globe.