Scientists have extended 2005 by one second - the first time in seven years that changes in the Earth's rotation have necessitated a "leap second", Reuters reports.

The extra snippet will be added to atomic clocks at midnight Coordinated Universal Time - the same as UK winter time - the US National Institute of Standards and Technology announced this week. Accordingly, said clocks will read 23:59:60 before rolling over to 00:00:00. The institute declared: "Enjoy New Year's Eve a second longer. You can toot your horn an extra second this year."

Although leap seconds could, if required, be deducted (a "negative leap second"), they have always been added "reflecting the Earth's general slowing trend due to tidal braking". The decision as to whether a leap second is needed - and the criterion is that universal timekeeping should be within 0.9 seconds of the Earth's rotation - is decided by the International Earth Rotation and Reference Systems Service. ®

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