Leap second adds more time to 30 June
The last leap second was added on June 30, 2012.
There will be a 61-second minute on Tuesday, June 30.
A leap second is a second which is added to Coordinated Universal Time (UTC) to synchronise atomic clocks with astronomical time to within 0.9 seconds.
This decision was made by the International Earth Rotation and Reference Systems Service, the global timekeeping body, in order to reconcile the atomic clock with the Earth’s rotation.
The reason a second is added every so often, is that Earth’s rotation around its own axis is gradually slowing down.
Atomic clocks, however are programmed to tick away at the exact same speed over millions of years.
Compared to the Earth’s rotation – which determines the length of a day – atomic clocks are simply too accurate.
The last leap second was added at 23:59:60 UTC on June 30, 2012.
Since 1972, a total of 25 seconds have been added. This means that the Earth has slowed down 25 seconds compared to atomic time since then.
This does not mean that days are 25 seconds longer nowadays. Only the days on which the leap seconds are inserted have 86,401 instead of the usual 86,400 seconds.
