… well, longer by 1 second that is. A leap second will be added on Saturday 30 June 2012 at 23:59:60 UTC (Coordinated Universal Time).
Leap seconds are occasionally inserted to keep UTC close to the mean solar time. By tradition, our clock time is related to the position of the Sun in the sky, which is in turn determined by the rotation of the Earth. But the Earth’s rotation rate is slightly variable, depending on factors like tidal friction and other processes which cause major mass redistribution. So Coordinated Universal Time (UTC) has been defined in order to keep the apparent position of the Sun in the sky, and hence our concept of the day, in line with International Atomic Time (TAI).
UTC is defined as being an integral number of seconds different from TAI so as to keep the Earth’s rotation linked with the day. This number of seconds is altered by one each time that the Earth’s irregular rotation has produced a difference amounting to a second.
These leap seconds are added (or subtracted) at either the end of the year (31 December) or halfway through the year (30 June).
The most recent leap second was added on 31 December 2008, and the one prior to that was on 31 December 2005.