The first dawn of 2017 will come a second late as India will join the rest of the world to add “one leap second” to its official time on the morning of January 1.
To account for earth’s slowing rotation around its own axis, time-keepers periodically add a leap second to universal time so that clocks remain accurate.
The adjustment is critical for applications like satellite navigation, functioning of communication networks, for tech companies and those conducting astronomical measurements.
As the leap second is added simultaneously across the world at UTC (Coordinated Universal Time) 23:59:59 hrs on December 31, 2016, New Delhi-based National Physical Laboratory (NPL), which maintains the Indian Standard Time will count up the additional second at 05:29:59 hrs on January 1, 2017. This is because the Indian Standard Time is 5.30 hours ahead of UTC.
“Last time, we did this on June 30, 2015. We do it time to time as per the international norm,” A Sengupta, who heads the time and frequency division at NPL told DH.
The earth’s rotation slows down due to several factors, including the moon’s gravitational pull.
The earth’s speed of rotation around its axis increases and decreases from time to time. This leads to a mismatch between Astronomical Time and the UTC maintained by a series of 300 highly precise atomic clocks, including the one at NPL.
The leap second adjustment is to correct the mismatch. Since 1972, 26 leap seconds have been added in intervals varying between six months and seven years.