While many will be glad to see the back of 2016 as soon as possible, this year will actually see a ‘leap second’ added to clocks around the world, making the year one second longer than usual.
The step is being taken in order to keep ‘civil’ time in step with ‘solar’ time, something that can fluctuate due to variations in the Earth’s rotation. Atomic clocks measure time much more accurately, and ‘leap seconds’ have to be added occasionally to ensure the sun is at its highest point at midday. The UK’s UTC timescale, which is managed by the National Physical Laboratory (NPL), will read 11.59.60 before 2017 officially begins.
“Atomic clocks are more than a million times better at keeping time than the rotation of the Earth, which fluctuates unpredictably,” said Peter Whibberley, senior research scientist in the Time and Frequency group at NPL.
“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.”
Fluctuations are measured by the International Earth Rotation and Reference Systems Service (IERS), based at the Paris Observatory. It announces about six months in advance when an adjustment is required. This upcoming leap second will mark the 27th time the UK timescale has been tweaked in this way, with the last occurrence taking place in June 2015. While the leap second is necessary, the importance of timing signals means there can be issues if the adjustment is not properly implemented.
“Because leap seconds are only introduced sporadically, they have to be manually programmed into computers and getting them wrong can cause loss of synchronisation in communication networks, financial systems and many other applications which rely on precise timing,” said Dr Leon Lobo, strategic business development manager for NPLTime.