For many, the end of 2016 can't come quickly enough.

But this longest of years is being stretched out a little further with an extra second being added just before midnight.

The 'leap second' is being tacked on to the end of the year to regulate the Earth's rotation with the UK's timescale.

Overtime, "Earth time" falls behind the atomic clocks kept by the National Physical Laboratory (NPL) that keep "civil" time.

An extra second is therefore occasionally added to regulate atomic and astronomical time.

Leap seconds typically occur every two or three years and the last one was inserted in June 2015.

Saturday night's leap second will be the 27th added since 1972

Peter Whibberley, Senior Research Scientist in the Time & Frequency Group at NPL, 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 a thousand years to accumulate a one-hour difference - if not corrected, it would eventually result in clocks showing midday before sunrise."