Friday 30 December 2016 02.00 EST NPL, based in Teddington, London, is Britain’s national measurement institute and the birthplace of atomic time.
The laboratory is responsible for providing the UK’s national time scale – known as UTC(NPL) – which is controlled by atomic clocks that are among the most accurate in the world.
Peter Whibberley, senior research scientist with NPL’s time and frequency group, said: “Atomic clocks are more than a million times better at keeping time than the rotation of the Earth, which fluctuates unpredictably.
“Leap seconds are needed to prevent civil time drifting away from Earth time.
Although the drift is small – taking around 1,000 years to accumulate a one-hour difference – if not corrected it would eventually result in clocks showing midday before sunrise.” The International Earth Rotation and Reference Systems Service (IERS), based at the Paris Observatory in France, tracks the Earth’s rotation and announces when a leap second is needed roughly six months in advance.