A ‘leap second’ has been added to the Indian clock at 5:29.59 hours on 1st Jan. to synchronise with the Earth’s rotational clock. The atomic clock at the National Physical Laboratory (NPL) has been programmed to add an extra second to 2017 to compensate for a slowdown in the Earth’s rotation.One second matters in the fields of satellite navigation,astronomy and communication. The Earth and rotation around its own axis is not regular, as sometimes it speeds up and sometimes it slows down due to various factors, including earthquakes and moon’s gravitational forces.Adding the leap second to the Indian clock is done by the NPL under the Council for Scientific and Industrial Research. The NPL, one of the oldest laboratories in the country, has five atomic clocks and nearly 300 such pieces exist across the globe.Atomic clocks are so precise that the margin of error in its functioning is just of a second in 100 million years.