In the nineteenth century, travel became easier and more rapid, particularly by rail. Railway timetabling made it increasingly impractical for every location simply to observe its own solar time, and various systems of standardization were proposed. On November 18, 1883, the American and Canadian railroad companies began to use a system devised by William F. Allen, in which North America was divided into four standard time zones.
Meanwhile, in Europe, some countries had already standardized time within their borders (though in a small country, this would not require multiple time zones), and proposals had been made for a global system of times zones. In 1884, the year after time zones were adopted by the railway companies in North America, Sir Sandford Fleming and others organized the International Meridian Conference in Washington, D.C. It was here that the Greenwich Prime Meridian was adopted as the center of international timekeeping, with twelve equal time zones extending to the East and West of the Greenwich Observatory. The International Date Line was also established on the other side of the globe.
It took many decades for all the countries in the world to adopt the international time zones, and anomalies continue to exist today. Perhaps the most striking is that China continues to use a single time zone across the whole country.