This Day in World History
October 13, 1884
Conference setting international time begins
Why does most every country in the world agree on how to determine what time it is? You can thank the International Prime Meridian Conference, which began on October 13, 1884, and lasted nearly ten days. The twenty-five countries that gathered in Washington , D.C., agreed to accept the line of longitude that passed through Britain’s Royal Observatory as the prime meridian—the line of 0° longitude (just as the Equator is 0° latitude). The nations also agreed that the time at Greenwich would be the standard time against which all other times would be compared—Greenwich Mean Time.
The conference was the brainchild of US President Chester Alan Arthur (in office 1881-1885), who recognized that the increases in international shipping and communication required the standardization of longitude measures and of time. Before 1883, when telegraph lines began transmitting time signals to all major US cities, there had been more than 300 local times in the United States.
The choice of Greenwich was hardly a surprise. Britain had used Greenwich mean time (GMT) since 1848 as the standard across its far-flung world empire, and the United States had adopted the same time zone system in 1883. The conference required unprecedented cooperation to overcome nationalist sentiments. France, ever Britain’s rival, proposed that the prime meridian should pass through the royal observatory in Paris, But in the end, Greenwich prevailed. While only two dozen nations took part in the agreement, others later adopted what would quickly become the global standard. And that is why, no matter where you are in the world, you will know what time it is.