what line of longitude forms the other side of the prime meridian

The line of longitude that forms the other side of the Prime Meridian (0° longitude) is the 180th meridian, also known as the antimeridian. It lies exactly opposite the Prime Meridian on the globe at 180° longitude, dividing the Earth into the Eastern and Western Hemispheres. This meridian often serves as the basis for the International Date Line, although the actual date line deviates in places to accommodate political boundaries