Is time running out for the leap second?

By Dave Gilbert, CNN

January 20, 2012 -- Updated 1234 GMT (2034 HKT)

The future of the leap second is being decided in Geneva.

STORY HIGHLIGHTS

More than 100 countries are discussing whether to keep the addition of leap seconds to the global time system
Many 21st century devices rely on incredibly accurate time keeping
The U.S. and most European nations want to abandon the leap seconds system which they say is too cumbersome
Without the adjustment, time measured by atomic clocks and time according to the Earth's rotation will start to deviate

London (CNN) -- Thursday could be a key moment in the future of time keeping.

More than 100 countries are due to decide on whether to keep the present method of adding so-called leap seconds to the global time system at the Radiocommunications Assembly in Geneva, Switzerland.

Currently, this Co-ordinated Universal Time or UTC is based on a system of extremely accurate atomic clocks. But they are so precise that they do not match the rotation of the Earth which periodically speeds up and slows down due to the action of the tides and changes within the Earth's core.

Since 1972 these extra seconds are added or taken away from the timescale to make sure UTC is synchronized with the Earth's rotation.

Fifty years ago, a few seconds difference had less impact but many of our 21st century devices depend on incredible accuracy.

Peter Whibberley, senior research scientist in the Time Group at the UK's National Physical Laboratory, explains that people like astronomers also rely on this level of precision.

"There are many applications today that depend on precise time keeping. For example, telecommunications use atomic clocks to keep the networks around the world synchronized precisely together," he said. "Satellite navigation -- sat navs in our cars and homes -- depend on signals being sent out from atomic clocks on board satellites."

But now many countries, including the U.S. and most European nations, want to abandon the procedure which they say is too cumbersome.

According to Whibberley, precise timing systems can be disrupted by altering them.

The UK, Canada and China are pressing to keep the leap seconds when the issue is discussed at the U.N.'s International Telecommunications Union meeting on Thursday.

"Without a correction, eventually our clocks would show the middle of the day occurring at night," said Whibberley. "We have to have some means of making a correction but at the moment no one knows how that's going to be done."

Since 1972 Whibberley said only 24 leap seconds have been used and the rate has slowed because the Earth has been speeding up over the last few decades.

Without the leap seconds adjustment, the precise time measured by atomic clocks and time according to the Earth's rotation will start to deviate.

Although the tiniest inaccuracies might play havoc with our smart phones most of us would not notice the changes in our body clock -- it is estimated it will take more than 200 years to register an hour's difference.