Details have been given in this Journal (Vol. 25, pages 3 2–42) of the new system of Coordinated Universal Time (U.T.C.) introduced on 1 January 1972. In accord with the agreed recommendations a positive leap-second was introduced at midnight on 30 June 1972 when the value of U.T.1–U.T.C. (DUT1) changed from −0s.64 to + 0s.36. However, the Bureau International de l'Heure has now announced that another positive leap-second is to be introduced at midnight on 31 December 1972, when (according to current estimates) U.T.1–U.T.C. will be about −0s.2; on 1 January 1973 DUT1 will thus be +0s.8, in excess of the maximum permitted value of of 0s.7.