Coordinated Universal Time (UTC) differs from international atomic time by an integral number of seconds and is the basis of most radio time systems and legal time systems. The step adjustments (leap seconds) are usually inserted after the 60th second of the last minute of December 31 or June 30. UTC is the time standard provided by WWV and other time broadcast services.

Barycentric Dynamical Time, Ephemeris Time, Greenwich Mean Time, International Atomic Time, Time, Universal Time