Timekeeping Authority to Eliminate Leap Seconds by May 2027, Ending Tech Infrastructure Headache

The International Bureau of Weights and Measures (BIPM) announced on Thursday that it will discontinue the practice of issuing leap seconds to adjust Coordinated Universal Time (UTC) starting May 20, 2027. The decision concludes three decades of debate within the metrological community, eliminating a periodic adjustment that has long caused synchronization disruptions across internet infrastructure, databases, and enterprise software systems, according to reporting by Wired (https://www.wired.com/story/leap-second-is-abolished-bipm-says/).

Leap seconds were introduced in 1972 to reconcile atomic-clock-driven UTC with Universal Time (UT1), which tracks Earth's astronomical rotation. Planetary rotation is subject to variation from tidal friction caused by the moon, atmospheric conditions, ocean movements, and dynamics within Earth's molten core. To keep UTC aligned with UT1, BIPM averages data from hundreds of atomic clocks worldwide and has inserted 32 positive leap seconds since 1972, most recently in 2016.

Because modern databases and network protocols rely heavily on continuous UTC timestamps, introducing a 61-second minute has frequently created software failures. Major platforms including Google and Meta developed custom "smear" methods to spread the extra second over roughly 24 hours in minute increments, as U.S. National Institute of Standards and Technology (NIST) fellow Judah Levine explained to Wired. However, unsmeared leap seconds have led to notable system failures, including the disruption of airline Qantas's booking system in 2012.

Operational concerns mounted further over the prospect of a negative leap second—subtracting a second from UTC rather than adding one. Earth's rotational speed has recently accelerated, partly due to melting polar ice shifting planetary mass, with a 2024 Nature study estimating that a negative leap second might have been required as early as 2029.

Tests conducted by an industry standards organization demonstrated widespread failures in systems subjected to simulated negative leap seconds. BIPM time department director Patrizia Tavella told Wired that the risk of a negative leap second drove the decision to establish the May 2027 deadline. Levine noted that while positive leap seconds presented operational challenges for 50 years, the effects of a negative leap second remained untested and posed significantly higher risks.

BIPM scheduled the change for May 20, 2027, to coincide with World Metrology Day and the anniversary of the 1875 Metre Convention that established the bureau. Tavella indicated that standard UTC-based software architectures will require no remediation, as systems can simply continue accumulating normal 60-second minutes. To handle the eventual cumulative drift between atomic time and Earth's rotation over millennia, BIPM also agreed in principle to establish a "leap hour," though such an adjustment remains thousands of years away.