NPL syncs Leap second with Indian time

An atomic clock at National Physical Laboratory (NPL) in New Delhi added ‘leap second’ (extra one second) to the Indian Standard Time (IST) at 5:29.59 hours on 1 January 2017 to synchronise with the Earth’s rotational clock.
The clock was programmed to add an extra second to the year 2017 in order to compensate for a slowdown in the Earth’s rotation.

Why extra second was added?leap-second-graphic-001

The Earth and rotation around its own axis is not regular, as sometimes slows down and sometimes speeds up due to various factors, including moon’s gravitational forces and earthquakes. As a result, astronomical time (UT1) gradually falls out of sync with atomic time (UTC). When the difference between UTC and UT1 approaches 0.9 seconds, a leap second is added to UTC through atomic clocks worldwide to match both times. Paris based International Earth Rotation and Reference System Service (IERS) tells when to add leap seconds on the basis of difference between UTC and UT1.


Adding leap second’ or second barely has an impact on the daily life. However, this one second shift is critical for applications requiring time accuracies in the nanosecond scale, which are critical in the fields of astronomy, satellite navigation, communication networks.


In India, leap second is added to the Indian clock by the NPL, Functioning under the Council for Scientific and Industrial Research (CSIR). The NPL is one of the oldest laboratories in the country, has five atomic clocks of the nearly 300 such pieces exist across the globe. Atomic clocks have high precision and the margin of error in its functioning is just of a second in 100 million years.


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