PARIS (Reuters) - By pure chance, Greece will gain fractionally more time to meet a midnight deadline on Tuesday to pay its IMF debts - thanks to a move by international time arbiters in the Paris Observatory to add one second to the world's clocks.

The so-called International Earth Rotation and Reference Systems Service charged with ensuring that earth time keeps pace with time measured by super-accurate atomic clocks ruled earlier this year that a tiny pause was needed to account for a gradual slowing-down in the earth's rotation.

The change, which will allow earth time to catch up with atomic time, will now take effect on Tuesday at the stroke of midnight Greenwich Mean Time, also known as UTC (coordinated universal time) in French.

"Very exceptionally, the minute ... will last one second longer than normal, that is, 61 seconds instead of 60," the Paris Observatory, which houses the international time service, said in a statement.

That literally gives Athens an extra second to either come to agreement with creditors over a cash-for-reform package that has already been five months in discussion, or otherwise find 1.6 billion euros owing to the International Monetary Fund.

"Yes, but one second isn't much time," Sebastien Bize, joint director of the Observatory's Space Time Reference Systems (SYRTE) arm, told Reuters TV. "And unfortunately, we can't add more than one second."

(Reporting by Lucien Libert; writing by Mark John)