UTC was officially formalized in 1960 by the International Radio Consultative Committee in Recommendation 374,[2] having been initiated by several national time laboratories. The system was adjusted several times until leap seconds were adopted in 1972 to simplify future adjustments. A number of proposals have been made to replace UTC with a new system that would eliminate leap seconds but no consensus has yet been reached.
The current version of UTC is defined by International Telecommunications Union Recommendation (ITU-R TF.460-6), Standard-frequency and time-signal emissions[3] and is based on International Atomic Time (TAI) with leap seconds added at irregular intervals to compensate for the slowing of Earth's rotation.[4] Leap seconds are inserted as necessary to keep UTC within 0.9 second of universal time, UT1.[5] See the "Current number of leap seconds" section for the number of leap seconds inserted to date.