On June 30, an extra second or 'leap' second will be added. NASA has stated that addition of leap second is important to compensate for earth's slowing rotation.

Experts have explained that a leap second is an extra second that is added to a day after every few years in order to ensure that Co-ordinated Universal Time (UTC), the world-standard for regulating clocks, remains in synch with Mean Solar Time.

As per which, the last minute UTC of June 30 will be 61 seconds. The National Research Council that keeps official time for Canada will be added the leap second in Canada. With the help of quit precise technique known as Very Long Baseline Interferometry (VLBI), scientists monitor how long it takes for Earth to complete a complete rotation.

On June 30, the clock will show 23:59:60 and then it will move to 00:00:00 on July 1. As per experts, when earth's rotation slows down, the time standards, UT1 and UTC, go out of the synch. Therefore, it is important to add an extra leap second.

For the first time, a leap second was added in 1972 and since then 25 leap seconds have been added. Experts said that leap seconds addition or subtraction depends upon whether earth's rotation slows down or speeds up.

The announcement for this week's leap second was added in January. Experts said that on an average, leap second happens after 18 months.