International Bureau of Weights and Measures votes to eliminate leap seconds
The bureau approved a change to Coordinated Universal Time that will replace occasional leap seconds with a leap hour, allowing up to one hour difference from astronomical time after 2027.
The International Bureau of Weights and Measures voted on Thursday to discontinue the use of leap seconds in Coordinated Universal Time (UTC). Since 1972, leap seconds have been added 27 times to keep atomic clocks aligned with Earth’s rotation, but the practice has become increasingly problematic for modern digital infrastructure.
Scientists and industry groups have argued that the occasional insertion of a one-second adjustment can disrupt telecommunications, satellite navigation, and power-grid synchronization. The new proposal would allow a discrepancy of up to one hour between UTC and astronomical time (UT1) before corrective action is required, effectively shifting to a "leap hour" that would be needed only about once every thousand years.
"The decision taken today reduces the risk to systems that depend on precise and continuous time synchronisation, including national infrastructure that we rely on daily," said Setnam Shemar, principal scientist at the National Physical Laboratory.
"Leap seconds can be difficult to implement reliably, and if not applied correctly they can cause differences in time across networks, potentially leading to the failure of systems such as mobile phone networks or electricity grids," Shemar added.
The change will take effect on 20 May 2027. While the link between UTC and UT1 will remain important for fields such as astronomy and celestial navigation, UT1 will continue to be monitored and its offset from UTC will be disseminated through existing international services.