Indian standard time leaps a second to catch up

NEW DELHI: A ‘leap second’ was added to the Indian clock at 5:29.59 hours on Sunday to synchronise with the Earth’s rotational clock.

As the atomic clock at the National Physical Laboratory (NPL) here struck 23:59:59 last night, it was programmed to add an extra second to 2017 to compensate for a slowdown in the Earth’s rotation.

While adding a second barely impacts everyday life, it does matter in the fields of satellite navigation, astronomy and communication.

“The Earth and its rotation around its own axis is not regular – sometimes it speeds up and sometimes it slows down due to various factors, including earthquakes and the moon’s gravitational forces. As a result, astronomical time (UT1) gradually falls out of sync with atomic time (UTC), and as and when the difference between UTC and UT1 approaches 0.9 seconds, a leap second is added to the UTC through atomic clocks worldwide,” said NPL director DK Aswal.

Adding the leap second to the Indian clock is done by the NPL under the Council for Scientific and Industrial Research (SCIR). 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.

To be in sync with the Indian Standard Time (IST) and the Earth’s rotational clock, the Indian clock need to be adjusted after the insertion of a leap second.

“The leap second adjustment is not so relevant for everyday life. However, this shift is critical for applications requiring time accuracies in the nanosecond like astronomy, satellite navigation,” Aswal clarified.