Establishing The Prime Meridian: Time To Talk About Time

By | March 7, 2022

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People looking at the Shepherd Gate Clock on the wall outside the gate of the Royal Observatory at Greenwich in south London. (The Print Collector/Getty Images)

A meridian is an imaginary line that runs from the South Pole to the North Pole. The Prime Meridian is so named because it was arbitrarily chosen as the line of 0 degrees longitude, or the starting point for measuring time and distance around the planet, but who put it there and why?

Before The Prime Meridian

In the past, each major country had their own prime meridian and their maps were made using that as the starting point, but as society became more global, non-standardized navigation maps became problematic. Time zones could change even from one city to the next, so folks missed their trains and merchants literally missed the boat. Recognizing the need for the world to come to an agreement about time zones, U.S. President Chester A. Arthur called for representatives of the world's countries to come together for an International Meridian Conference, held in Washington, D.C. in 1884.

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President Chester A. Arthur in 1884. (Catalog of American Portraits/Wikimedia Commons)

The International Meridian Conference

In all, 26 countries were represented at the conference, and although everyone agreed on the need to establish a global prime meridian, they didn't agree on where it should be. After some debate over the merits of the lines crossing through Rome, Paris, Oslo, St. Petersburg, Jerusalem, and more, the group settled on the one bisecting the Royal Observatory in Greenwich, England, with 24 time zones increasing by one hour as they move east and decreasing to the west.

The International Meridian Conference also passed seven key resolutions, including the International Date Line, universal solar day, and the standardization of navigation charts. These resolutions were accepted by most countries, but there are a few notable exceptions. For example, China is nearly as wide as the United States, but it operates on one time zone rather than the four found in the continental U.S.