Tonight June 30, 2012, it will take a second longer to go to July 1st! Indeed, the lastminute of the day will not 60 seconds but 61 seconds to correct a gap in timebetween the rotation of the earth and universal time counted by atomic clocks.
This is not the first time this has happened, but the world must put the record straight somehow! The latest dates from December 31, 2008. The reason for this correction for the least surprising, is that our time is defined by atomic clocks, but the reality is much less accurate, that the regularity of the cesium atom (one ten-billionth of a second) which is based on universal time.
To make it simpler, the rotation of the earth is not constant as one might think she would even tend to slow down, due to its position in space relative to the moon, under the influence of tides and even during earthquakes … However, atomic clocks use the amazing regularity of the cesium atom to beat the time. A small gap is widening between the two then, and when this gap is at 0.9 seconds, the scientific application to the correction and it is the International Department of Earth Rotation and Reference Systems Service (IERS), which undertakes this task in the world.
This kind of correction is traditionally done on June 30 or December 31 and it is particularly important for technology, GPS, astronomy, etc.. Because the slightest deviation can result in some areas of errors or malfunctions. Level of everyday life, nothing will change except that it will take one more second before midnight does not ring!