Time zones Summary

  • Last updated on November 10, 2022

The development of standard time and the division of the continental United States into four time zones allowed work and transportation schedules to be rationalized, helping drive the development of the United States as an industrialized society.

Time zones are industrial humanity’s method of dealing with the Sun’s illuminating a round, rotating Earth. While a person in Chicago observes high noon, a person in London is observing sunset, a person in Honolulu is observing sunrise, and a person in Mumbai, India, is using artificial light to illuminate the night. So long as travel and communications were slow and primitive timekeeping devices were inaccurate, this phenomenon remained of academic interest. Its first practical use was in open-ocean navigation, to solve the problem of determining longitude.Time zones

In the nineteenth century, the telegraph and the railroad enabled messages and people to travel at previously unimaginable speeds. European countries gradually instituted standardized time, placing the entire country on the solar time of the capital. However, such a solution would not have been practical for a nation as large as the United States. San Francisco’s observed time would lag three hours behind official time from Washington, D.C. American railroads developed systems of time zones that allowed each region’s standard time to remain reasonably close to observed solar time. However, this “railroad time” was not coordinated among the various railroad companies, leading to incompatible schedules: Major railroad stations had to display a different clock, indicating a different time, for each railroad company using that station.

In 1882, the heads of the various railroads met in St. Louis, Missouri, and worked out a system to divide the United States into four standard time zones. Each zone would be centered on a meridian of longitude 15 apart, because 15 represents one-twenty-fourth of the full 360 circle of Earth. Thus, each zone would be one hour wide. This system went into effect the following year. However, Americans resisted the institution of standardized time zones for years before they became widely accepted throughout American culture. In one town, a man who persisted in using local solar time in defiance of standard time protested being fined for contempt of court when he failed to appear at the “correct” time for a noon court date.

In 1884, Congress passed a resolution authorizing President Chester A. Arthur to call the International Meridian ConferenceInternational Meridian Conference. Although the meeting was held in Washington, D.C., the Greenwich, England, meridian was chosen as the zero point for the international time system. It was established practice in the English-speaking world to use that meridian as the zero meridian of longitude. This time zone was termed Greenwich mean time (GMT), or universal time. The conference then established twelve time zones on each side of the prime meridian, as well as the international date line in the Pacific Ocean. In actual practice, the system of time zones has become an odd patchwork, as various polities have pushed and pulled the boundaries of the time zones away from the ideal arrangement to avoid cutting communities in half.

Further Reading
  • Barnett, Jo Ellen. Time’s Pendulum: From Sundials to Atomic Clocks–The Fascinating History of Timekeeping and How Our Discoveries Changed the World. San Diego: Harcourt Brace, 1999.
  • Dolan, Graham. The Greenwich Guide to Measuring Time. Chicago: Heinemann Library, 2001.
  • Kern, Stephen. The Culture of Time and Space, 1880-1918. Cambridge, Mass.: Harvard University Press, 2003.

Daylight saving time

Metric system

Railroads

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