A positive leap second will be introduced at the end of June 2012.
The sequence of dates of the UTC second markers will be:
2012 June 30, 23h 59m 59s
2012 June 30, 23h 59m 60s
2012 July 1, 0h 0m 0s
The difference between UTC and the International Atomic Time TAI is:
from 2009 January 1, 0h UTC, to 2012 July 1 0h UTC : UTC-TAI = - 34s
from 2012 July 1, 0h UTC, until further notice : UTC-TAI = - 35s
Leap seconds can be introduced in UTC at the end of the months of December
or June, depending on the evolution of UT1-TAI. Bulletin C is mailed every
six months, either to announce a time step in UTC or to confirm that there
will be no time step at the next possible date.