

A leap second is sometimes added to bring Atomic Time -- a near-perfectly accurate way to score seconds by measuring the vibrations of atoms -- into sync with the Solar Time spin of the Earth -- which is irregular, and gradually slowing down.

When the two time-keeping methods veer apart by a second, an extra second is added in June or December to delay Atomic Time and bring it in line with Solar Time. One was added in December 2008, and another is due to be inserted in June 2012.

It's just like the leap year, where every four years a bonus day is introduced to account for the discrepancy between our 365 day year and the Earth's 365 and a quarter day rotation around the Sun.

You probably won't notice the extra second in June 2012, but it will be a major headache for those running the internet, telecommunications, or any kind of computerised system. It's for that reason that some countries -- including America and France -- want it gone.

But fans of the leap second -- such as Britain and Germany -- argue that without it, Atomic and Solar Time would veer further and further apart. Time could be two to three minutes out in the year 2100 and about half an hour wrong in 2700. 

It's this back-and-forth argument that stopped the world's top time-keepers from coming to an agreement. The ITU has decided that more research was needed to understand the social, legal and technical implications of removing a leap second. Once that's been collected, everyone will meet up in 2015 to argue all over again.

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