Since 1972, leap second has been added 35 times. Yet again on June 30, Tuesday, a leap second will be added. Just before midnight Coordinated Universal Time, one second will be added to our clocks.

Explaining the reason as to why there is a need to add a second, Terry Jones, an astrophysicist with the University of Minnesota, said, "The Earth's rotation is slower than it used to be because the Earth is slowing down, so every few years we have to add an extra second to keep the sun and time that we keep with our clocks lined up".

Our watches are set as per atomic time. Therefore, it is important to update them time to time. Coordinated Universal Time (UTC) is said to be the chronological standard that regulates the world's official clocks. It requires adjustment for earth's irregular rotation.

Experts said that earth's rotation is slowing because of tidal forces between earth and the moon. Jones said when the moon orbits earth, it pulls tides up and down causing friction that makes earth to slow down. Therefore, earth is moving bit slow than what it used to be.

Jones said that one rotation of earth should take 86,400 seconds to rotate each day, but its average is closer to 86,400.002 seconds. The idea of adding leap second is not suitable to everyone. It has been said as the extra second is known to negatively impact computer system and websites.