World Metrology Meeting to Vote on Abolishing Leap Seconds by 2027

Timekeeping officials are gathering in Versailles, outside Paris, to vote on a proposal that would end the practice of adding leap seconds to Coordinated Universal Time (UTC). The decision could be taken as early as Thursday and, if approved, would take effect on May 20, 2027, World Metrology Day.

Leap seconds have been inserted since 1972 to keep UTC in sync with the Earth’s irregular rotation, with the most recent addition on Dec. 31, 2016. The International Bureau of Weights and Measures (BIPM) is considering three proposals: redefining the second using optical frequencies, eliminating the leap second, and aligning Earth-based timekeeping with a new lunar time standard under development by NASA.

"The speed of the Earth’s rotation is not constant. This gradual decrease in the rotational rate is causing the duration of the mean solar second to gradually increase with respect to the atomic second," the U.S. National Institute of Standards and Technology (NIST) explained.

Industry groups have raised concerns that leap seconds can cause system failures; LinkedIn and Reddit experienced outages after a leap second in 2012, and Meta engineers described them as "a major source of pain for people who manage hardware infrastructures." Proponents of scrapping the leap second argue that removing it would prevent such disruptions in financial markets, data centres and other time-sensitive operations.

If the leap second is abolished, clocks would no longer track Earth’s rotation, requiring adjustments to legacy systems that rely on UTC for astronomical observations. Some scientists suggest larger, less frequent corrections such as "leap hours" could be introduced instead. Over centuries, the divergence would grow, potentially reaching a 54-second difference by 2100 and several hours over millennia, affecting the alignment of sunrise and sunset times with daily routines.