Scientists say clock discrepancies could cause problems in the future if we didn't insert these occasional corrections...
We will all have a little more time to celebrate this New Year's Eve, as scientists are adding a leap second at the stroke of midnight.
The extra second is being added to ensure our electronic clocks are in sync with the Earth's rotation. More specifically, it aims to correct differences between Universal Time (UT1) and International Atomic Time (TAI).
26 leap seconds have been inserted since 1972, and tonight's will occur at 23:59:60.
While clocks normally goes from 23:59:59 to 00:00:00, the extra second is being added in between - and hi-tech digital clocks will record that time as 23:59:60.
National Standards Authority of Ireland (NSAI) Meteorologist Dave Fleming explained what would happen if scientists did not take this step.
"The Earth is slowing down," he explained. "Very gradually, but it's slowing down enough that so that it could cause problems in the future if we didn't insert these corrections once every so often.
"If the two systems were to diverge, ultimately hundreds of years from now the sun will start rising earlier in the sky; solar noon wouldn't be around 12 o'clock; so it's just to keep everything in sync".