Leap Second On New Year's Eve: What Happens If We Don't Add Another Second To World's Clocks?


2016 will be a bit longer because a leap second will be added to the world's clocks on New Year's Eve.

One second isn't that long. People can't do much within this time frame but why bother extending the time with an additional second?

Clocks May Eventually Show Midday Before Sunrise

Leap seconds are added to keep the clocks in sync with the Earth's fluctuating rotation. Time was historically based on the position of celestial bodies such as the changing shapes of the moon and the rising and setting of the sun.

Universal Time, as this is called, is governed by the gravitational motions of the Earth, moon and sun but since the 1960s, time has been measured by atomic clocks that are independent of planetary motion. Unfortunately, the planet does not keep perfect time. The rotation of the Earth decelerates and is gradually slowing down.

Findings of a study published in the journal Proceedings of the Royal Society A, have shown that the spin of the Earth on its axis has slowed down by 1.8 milliseconds per day over the course of a century, which is why the two systems of time do not always line up. Something needs to be done to keep them in sync.

Peter Whibberley, from the National Physical Laboratory in the UK, explained that the extra second is needed to prevent time from drifting away from Earth time. The drift may be small requiring a thousand years to result in a one-hour difference but if this is not corrected, clocks would eventually show midday before sunrise.

Computer Systems Need To Accommodate Extra Second

Computer systems that rely on time need to come up with a way to accommodate the additional leap second. Otherwise, the extra second can cause problems. Google uses "leap smear," where it gradually adds milliseconds to its system clocks before the official arrival of the leap second, to avoid problems associated with the extended time.

Back in 2012, sites that include Yelp, Reddit and LinkedIn went down because of the extended second. Airline passengers were also stranded because of software glitches traced to the extended time.

Many computing systems use networking protocol to synchronize with the world's atomic clock but when an additional second is added, some of these systems do not know how to handle it. In 2012, affected servers halted when they failed to properly accommodate the leap second that was added to the world's atomic clocks.

The problem when leap seconds are added in computers is that the systems can see the extra second as a time going backward that can be interpreted by machine registrars as a system error which can overload the CPU.

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