Earth Still Stable

14 Jan 2005

The International Earth Rotation Service (IERS) has just announced that there will be no need to adjust watches and clocks at the end of June.

Civil timescales, such as Greenwich Mean Time in Britain or Mountain Standard Time in the USA, are maintained using atomic frequency standards. So-called "leap seconds" are sometimes necessary to maintain reasonable coherency between the time maintained by these relentlessly constant atomic clocks and the Earth's somewhat variable, rotational time.

Since we can't adjust the speed of the Earth's rotation, civil time is periodically adjusted in one second steps to maintain a difference of no more than 0.9 seconds. The adjustment, if necessary, occurs on the last day of June or December. The IERS has determined that the world's rate of spin is not significantly changing at present and so no leap second is needed.

• The Leap Second explained (by NPL)
• IERS