The world will add an additional second to the clocks at the stroke of midnight on New Year’s Eve. This means the last minute of 2016 will be 60+1 seconds long.
This addition of “leap second” at 23 hours, 59 minutes and 59 seconds Coordinated Universal Time (UTC) will be the set as the new time standard by highly precise atomic clocks.
Why bother with one second?
The extra second of time is being added to align two ways of keeping time: clocks based on Earth’s rotation and the atomic clocks.
Demetrios Matsakis, Chief Scientist at the U.S. Naval Observatory’s Time Service Department, talked about this last year,
“Earth is slowing down over geological time, and that can lead to a problem when you’ve got a ton of clocks. What do you do when the day gets longer?”
Previously time was measured using the rotation of the Earth in relation to distant celestial objects, but it was discovered that moon’s gravitational pull slows down our planet’s spin. So this method was termed imprecise.
Then almost a century back, time keeping was turned to atomic clocks, which use vibrations of atoms to keep track of time. These are so frighteningly precise that the scientists estimate they will not lose a second of time for the entire age of the universe.
The current official atomic clock is placed in the United States and uses the vibrational frequency of the cesium atom to base one second.
But since the earth loses the rotation-based time each day due to the moon centered tug, about 1.5 and 2.0 milliseconds to be exact, a relative difference between the time of the gravitational clock and the atomic clock is induced. This discrepancy racks up to a whole second after every 500 to 750 days, so to keep these two times in sync, the practice of adding a leap second is followed.
In fact, the International Earth Rotation and Reference Systems Service (IERS) has been performing this ritual since 1972, and up till now, the world has seen 26 such leap seconds. The last bonus second was added on June 30, 2015, and are usually added on either June 30 or Dec. 31, according to the IERS.
Leap seconds can pose a headache for many communication networks, financial corporations, and other applications that rely on precise timing. In 2012 this addition caused a glitch in the software running Reddit, Gawker, and other websites, but this time the companies claim that they are far better prepared.