Prime meridian is the name of the line that marks 0 degrees of longitude. The prime meridian marks the beginning reference point for making measurements in the eastward and westward directions. Any location along the prime meridian serves as a starting point for measurements, although international consensus designates the city of Greenwich, England as the official prime meridian.
Despite forming a mutual consensus appointing Greenwich as the official prime meridian, governments of countries worldwide historically disagreed on the actual location marking the prime meridian. Any point on the line of 0 degrees longitude qualifies unofficially as a prime meridian. Lack of consensus on a true prime meridian posed problems for cartographers, navigators and city officials.
In 1884, representatives from various countries convened at the Royal Observatory in Greenwich, England. They agreed on forming a standard line of prime meridian; the center ran through the middle of the Royal Observatory, previously a working scientific facility. In addition to marking 0 degrees east and west, the prime meridian establishes Universal Coordinated Time, or UTC. Countries worldwide use UTC to set regional time zones within their borders. Additionally, the prime meridian divides the world, along with the International Date Line, into the Eastern and Western Hemispheres.