The almost perfect circle ( the earth is an oblate spheroid that is fatter around the equator ) , drawn with a line , demarcating the Eastern and Western Hemispheres must be an arbitrarily decided and published convention , unlike the equator ( an imaginary line encircling Earth , equidistant from its poles ) , which divides the Northern and Southern Hemispheres . The prime meridian at 0 ° longitude and the antimeridian , at 180 ° longitude , are the conventionally accepted boundaries , since they divide eastern longitudes from western longitudes . This convention was established in 1884 at the International Meridian Conference held in Washington , D.C. where the standard time concepts of Canadian railroad engineer Sir Sandford Fleming were adopted . The Hemispheres agreed do not correspond with exact continents . Portions of Western Europe , West Africa , Oceania , and extreme northeastern Russia are in the Western Hemisphere , divorcing it from the continents which form the touchstone for most geopolitical constructs of " the East " and " the West "
International Meridian Conference
International Meridian Conference
Eastern Hemisphere