The Prime Meridian passes through the continents of Europe, Africa and Antarctica. This imaginary line is located at 0 degrees longitude. The Prime Meridian and International Date Line divide the Earth into the Eastern and Western hemispheres.
The official Prime Meridian was chosen at an international convention in 1884 to be the line that runs through Greenwich, England. Before then, most countries set the Prime Meridian as the line that ran through the capital city. It sets the Coordinated Universal Time, in which all 24 times zones in the world base their measurements. The Prime Meridian was also used to establish the International Date Line, which is located at 180 degrees longitude.