This week the ITU Radio Assembly in Geneva are discussing whether to abolish leap seconds and the National Physical Laboratory (NPL) has released a video discussing the issue.
Time was long measured using the sun with a mean solar day being 24 hours. That was good enough then, although a solar day was not highly accurate due to variations in the earth's rotation.
That changed in 1955 when an atomic clock was developed that measured the vibration of an atom of caesium, leading to the adoption of International Atomic Time.
However this resulted over decades in differences between Atomic Time and solar based Universal Time (UT) and since 1972 it has been the practice to periodically re-synchronise them, by way of inserting a leap second. These leap seconds are added either at the end of June, or December, however, this appears to be too difficult for some countries and there is an attempt at this week's ITU meeting to eliminate them.
