New Year arrived a bit later than normal this year because the speed at which the Earth turns is slowing down. A “leap second” was be added to the end of 31 December and 2006 started at one second past midnight. A day is about two thousandths of a second longer than it was 200 years ago, mainly because tides are causing the Earth to spin more slowly. Leap seconds keep the clocks in time with the Earth and the Sun, but this is the first to be used for seven years. The decision was taken by the International Earth Rotation and Reference Systems Service, based at the Paris Observatory.