What is a Leap Second?

June 30th, 2012 will be longer by a Second! That means your weekend is going to extend for one more Second! What does that mean? 


Global time keepers are adding One Second to UTC (Coordinated Universal Time) which is often referred as Greenwich Mean Time (GMT). This added Second is called the Leap Second

Why are the Leap Seconds added?
The Earth's rotation around its own axis determines the length of the day. This rotation of the Earth is slowing down very gradually and at an unpredictable pace. The gravitational pull of ocean tides, the sun and the moon all affect its rotation ever so slightly. According to the US Naval Observatory, our planet is decelerating by about 1.4 milliseconds per day each century. 
So, leap seconds are a means to adjust our clocks to the Earth's slowing rotation.


How many Leap Seconds have been added till now?
This adjustment began in 1972 by The International Earth Rotation and Reference Systems Service (IERS) . A total of 24 leap seconds have been added to the clock since. This will be the 25th Leap Second 


When are the Leap Seconds added?

Leap seconds are inserted at the end of the last day in June or December. When that is the case, UTC ticks from 23:59:59 to 23:59:60 before reverting to 00:00:00 (in the 12-hour format, this corresponds to 11:59:59 pm - 11:59:60 pm - 12:00:00 midnight). When that happens the last minute of the month has 61 instead of 60 seconds.