TIME came to a brief "standstill" around the planet last night because the Earth is turning too slowly.
Today was delayed by one leap second, added at midnight GMT (1 a.m. BST) to allow atomic clocks, which keep the Earth's official time, to be re- synchronised with astronomical time.
"The Earth has been turning too slowly," said Mr Martine Feissel, director of the Paris-based International Earth Rotation Service (IERS), which decides every six months if the world needs to add or subtract a second.
Friction from winds and tides and changes in the structure of the Earth's core all contribute to slowing the Earth's rotation, which is measured astronomically by reference to star positions.
But atomic clocks do not function at the same rate as the Earth rotates, which means they must be adjusted from time to time.
The Earth takes one or two milliseconds longer to rotate on its axis in February than in August, and an average day in 1994 was two milliseconds longer than in 1987.
When the fluctuations due to the discrepancy between astronomical and atomic time produce a gap exceeding 0.9 seconds, the IERS imposes a leap second.
The change affects everything that is synchronised by satellites - from communication, navigation and air traffic control systems to the computers that link financial markets. Scientists must account for the discrepancy because the cumulative effect would mean that over a century a clock would gain several minutes