In October 1884, the International Meridian Conference at Washington DC adopted a proposal which stated that the prime meridian for longitude and timekeeping should be one that passes through the centre of the transit instrument at the Greenwich Observatory in the United Kingdom (UK).
GMT was superseded as the international civil time standard by Coordinated Universal Time (UTC) in 1960, when the International Radio Consultative Committee formalized the concept of Coordinated Universal Time, abbreviated as UTC.