Leap second could be abolished The leap second was first introduced in 1972 and since then has been used on 24 occasions to keep astronomical time - which is based on the rotation of the Earth - in line with international atomic time, based on the movements of a caesium atom, which goes like, well, clockwork. Britain's Royal Observatory, among others, are happy with the leap second but opponents, including the International Bureau of Weights and Measures in Paris, are pressing for it to be dropped. Jonathan Betts, senior curator of horology at the Royal Observatory, told the Independent: "We think this would be a shame. We feel that it's important not to lose the link between the measurement of time and the Sun, which after all has been fundamental to the human timescale. It would disconnect us from nature, which is not what people want. Those in favour of abolishing the leap second argue that many critical systems, such as the GPS instruments used in aircraft navigation or computer-trading systems used in international finance, depend on highly accurate timekeeping, which might fail if people forgot to update them. The next leap second, which might be the last, will be added to the midnight signal on 30 June 2012.