In October 1884 the Greenwich Meridian was selected by delegates ( forty-one delegates representing twenty-five nations ) to the International Meridian Conference held in Washington , D.C. , United States to be the common zero of longitude and standard of time reckoning throughout the world . The modern prime meridian , the IERS Reference Meridian , is placed very near this meridian and is the prime meridian that currently has the widest use
International Meridian Conference
International Meridian Conference
Prime meridian