World timekeepers vote to abolish leap second by 2027

International delegates have voted to scrap the leap second, ending a 50-year practice that kept atomic clocks aligned with the Earth’s rotation. The decision was made on Thursday, October 15, at a conference of the International Bureau of Weights and Measures (BIPM) in Versailles, France, with 69 member states casting votes.

Leap seconds have been added 27 times since 1972 to reconcile coordinated universal time (UTC), measured by ultra-precise atomic clocks, with astronomical time, which is based on the Earth’s uneven rotation. The extra second was typically inserted at the end of June or December.

While the adjustment is imperceptible in daily life, it has caused significant problems for modern technology. A leap second crashed Reddit and LinkedIn in 2012, and Cloudflare suffered brief outages in 2016. Tech giants including Meta, Google, and Amazon have long campaigned against the practice, calling it “a major source of pain.”

Under the new system, UTC will be allowed to drift up to one hour from astronomical time before a “leap hour” is applied. The change takes effect in May 2027.