The last leap second was added at 23:59:60 in coordinated universal time on june 30, 2012.

Since 1972, a total of 25 seconds have been added. This means that the Earth has slowed down 25 seconds turning.

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.