The planet’s timekeepers added an extra second to the clock at midnight universal time Saturday night. The so-called leap second was needed to synchronise the world’s official atomic clocks, said John Lowe, who heads the time and frequency services group at the National Institute of Standards and Technology. The reason? Earth is spinning just a bit slowly. The time it takes Earth to rotate on its axis — which is the definition of a day — is now about two milliseconds longer than it was 100 years ago, said Geoff Chester, spokesman at the US Naval Observatory, in an interview with the Associated Press. Over the course of a year, that adds up to nearly three-quarters of a second.
