The International Earth Rotation and Reference Systems Service (IERS) has announced that a leap second will be added to Coordinated Universal Time (UTC) at the end of 2016. This will be the 28th leap second added to UTC since 1972, and it will take the difference between International Atomic Time (TAI) and UTC to 37 seconds.
The procedure of insertion of a second to UTC has been implemented since 1972 to approximately correct the increasing offset between UTC (an atomic uniform time scale) and the time derived from the non-uniform rotation of the Earth (namely UT1). The IERS is responsible for the announcement of leap second insertions, following a procedure described in a recommendation adopted by the Radiocommunication Sector of the International Telecommunication Union (ITU-R). By this process, the value of UT1-UTC is kept below 0.9 s.
The Bureau International des Poids et Mesures (BIPM) is responsible for the computation and dissemination of UTC on the basis of readings of atomic clocks maintained by about 80 national institutes located around the world.
UTC has been adopted by the ITU-R as the international reference for standard-frequency and time- signal emissions, and is the basis of most legal times. The global navigation satellite systems (GNSS) such as GPS (USA), GLONASS (Russian Federation), Galileo (Europe) and BeiDou (China) realize internal atomic system times which are closely synchronized to UTC, even if almost all of them avoid leap second insertions.
Leap seconds are inserted in all the atomic clocks representing UTC at exactly the same time. The next one will occur on 31 December 2016, following the 23 h 59 m 59 s of UTC. This will present clocks and time servers with the challenge of realizing a 61-second last minute of the year.