Leap Second on 30th June 2015
30 January 2015
This leap second will be the 26th leap second since the leap second procedure was introduced on 1 January 1972.
Leap seconds are inserted because the mean solar time and the atomic time vary due to fluctuations in the rotation speed of the earth and slowing of the earth’s rotation from friction caused by ocean tides and the atmosphere. This results in the two timescales varying.
A debate has been going on for a number years about whether to abolish the leap second procedure and just allow the UTC to gradually drift away from solar time or to find some other solution but agreement on a solution still appears to be some way off.