People who are desperately waiting for the year 2016 to end might have to wait a little longer.
At the last minute of the year 2016, an extra second will be added to the UTC (Coordinated Universal Time) clock. This means the clock will go from 23:59:59 to 23:59:60 to 00:00:00. In India, it will happen at 05:29:60 on 1st January 2017. The extra second was last added on 30th June 2015.
A screengrab of the UTC clock from the www.time.gov website during the leap second on June 30, 2015.
The extra second added is popularly known as a leap second, which is added from time to time on the recommendation of International Earth Rotation and Reference Systems Service (IERS). The IERS submit a bulletin called Bulletin C every six months to confirm the leap second at the next possible date.
The latest Bulletin C regarding the 31st December 2016 leap second. Source: IERS
The bulletin mentions TAI, what is that?
The TAI (Temps Atomique International, which translates to International Atomic Time in English) is the “weighted average of the time kept by over 400 atomic clocks in over 50 national laboratories worldwide”. These atomic clocks are highly accurate and known to have an error of 1 second in up to 100 million years.
They are managed by the International Bureau of Weights and Measures (BIPM) and help in maintaining correct UTC. TAI is currently 36 seconds ahead of the UTC and will be 37 seconds ahead of UTC from 1st Jan 2017 00:00:00.
This is because TAI does not consider leap seconds into its calculations as the TAI atomic clocks are continuously working and independent of Earth’s rotation speed (we discuss this below). Instead, a second is added or removed from UTC.
Why do we have leap seconds?
People might be familiar with leap year; the extra day added almost (yes, almost) every four years in the month of February. It is because the Earth takes about 365.242189 days to make one complete revolution around the Sun and we balance it out in the fourth year.
Similarly, to balance out the fast or slow rotation of the planet Earth we add or remove the leap second from the UTC. The imbalance of rotation speed is caused by various factors such as Moon’s gravitational Earth-braking forces and El Niño climate cycle.
This fast or slow rotation is determined by the Universal Time (UT1), sometimes called as Astronomical Time, refers to Earth’s one complete rotation around its own axis.
When the difference between UT1 and UTC approaches towards 0.9 seconds, a leap second is added to UTC by the IERS.
Leap seconds has caused many problems in the past. The addition of leap second on 30th June 2012 led to crashing of Qantas Airlines and Reddit servers.
Cover Image: Source
Kshitij runs The Patil Post and Zetabyte Solutions Pvt. Ltd. - a web development company focussed on E-Commerce implementations. Loves to eat, sell, write and talk. He is an avid reader, an enthusiastic traveller and trekker at heart.
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