The clocks all over the world will have to be slowed down simultaneously by one second to accommodate this extra second which arises due to a difference between the international time standard and the traditional astronomical time based on earth's rotation.

Says P Banerjee, a senior scientist from the time and frequency division at National Physical Laboratory (NPL), "Just before the clock ticks away into the final year of this millennium on December 31 it will read 23h:59m:59s. After one second the reading will be 23:59:60 and yet after another second it will be 00:00:00 of 1999."

This adjustment, known as `leap second', was necessary to carry out high-precision scientific studies like astronomical and geological observations correctly, he adds.

In fact a specially designed software has been incorporated into NPL's cesium atomic clock for carrying out the correction measures as NPLbears the responsibility of maintaining the Indian Standard Time (IST).

The concept of leap second adjustment came into being after the discovery of cesium atomic clocks (which have a chance of loosing one second after a continuous run of 10,000 years) for international timekeeping.