Earth’s Rotation Accelerates: Metrologists Propose Ending Leap Seconds and Introducing Leap Hours
The International Bureau of Weights and Measures (BIPM) is planning a vote on October 15, 2022, to potentially eliminate the leap second, which has been added 27 times since 1972 to keep Coordinated Universal Time (UTC) aligned with astronomical time (UT1). This adjustment has historically corrected discrepancies caused by irregularities in Earth’s rotation. However, recent measurements show Earth spinning faster, possibly leading to a negative leap second with about a 30% chance over the next ten years, according to Sethnam Shemar, Chief Scientist at the UK’s National Physical Laboratory.
Over the past five decades, UTC and UT1 have diverged by a total of 27 seconds. If this gap ever exceeds 3600 seconds, scientists may introduce a leap hour to realign time standards. From May 20, 2027, a difference of up to one hour between UTC and UT1 will be tolerated without adjustment, allowing for greater continuity of UTC over centuries or longer.
“Starting May 20, 2027, a tolerance of one hour will be accepted before any intervention is needed, ensuring UTC’s smooth operation for centuries or more.” — Sethnam Shemar
Even if leap seconds are discontinued, UT1 will still be monitored and disseminated by international services to support astronomical observations and navigation. This shift would mark a significant change in how time is measured, addressing the challenges posed by Earth’s faster rotation.
Removing leap seconds could have major implications for systems that rely on precise timing, including navigation, telecommunications, and financial markets. The potential future adoption of leap hours aims to offer more flexibility but will also require updates to modern technologies and protocols. Continued observation of Earth’s rotation remains critical for science, underscoring the importance of accurate timekeeping amid natural changes.