How was the Prime Meridian established at Greenwich?

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World time zones: Each color represents a different zone.

The International Meridian Conference in 1884 was the event that finalized the establishment of the Prime Meridian. It was actually the third out of three international conferences about the Prime Meridian.

  • The first was in 1871 at Antwerp, and it was called the International Geographical Congress (IGC). It was suggested that Greenwich should be adopted as a common zero longitude for all sea charts, and that this should be required within 15 years. This would not apply to land maps and coastal charts, which would use their country's original meridian. Although they discussed this topic at great length, they came to no conclusions.
  • The whole matter was brought up yet again in the second IGC during 1875 in Rome, Italy. France reasoned that if the Prime Meridian were to be established at Greenwich, Great Britain should adopt the metric system. Although it was debated over for a long while, there were still no conclusions drawn to solve the issue.
  • The third and final part of this debate was the International Meridian Conference (IMC) in Washington D.C., on October 13th, 1884. Forty-one delegates from 25 different nations attended the conference, including Sir Sanford Fleming of the UK, the well-known inventor of standard time, or the 24-hour-clock. It was his ideas about time zones that influenced countries to believe in the need for a prime meridian to replace the many meridians already in existance.

At the IMC, Greenwich's main opponents were Washington D.C., Paris, and Berlin. During the conference, the US decided to back the Greenwich Meridian, and soon after Berlin followed.
Twenty-one out of 25 countries voted for locating the Prime Meridian through Greenwich Observatory. France and Brazil did not vote, and San Domingo was the only country that voted against it.

At this conference, it was concluded that:
  • Longitude would be calculated east and west of the meridian up to 180 degrees;
  • All countries would adopt a single day beginning at midnight at Greenwich using a universal clock;
  • The Prime Meridian would pass though Greenwich Observatory in the Greater London Area.


By Caroline Lucas and Jade Mulcahy