Leap Second Abolished, Allowing Clocks to Drift Up to an Hour
International decision aims to reduce risks to digital infrastructure from timekeeping inconsistencies.
In a significant shift for global timekeeping, scientists have voted to eliminate the "leap second," a practice that has synchronized Coordinated Universal Time (UTC) with Earth's rotation for over 50 years. The decision by the International Bureau of Weights and Measures (BIPM) allows for a divergence of up to one hour between atomic time and astronomical time.
The change, approved by a majority at the General Conference on Weights and Measures in Versailles, France, is set to take effect on May 20, 2027. This reform aims to mitigate risks to digital infrastructure that have arisen from the complexities of implementing leap seconds.
Leap seconds are adjustments of one second added or removed from UTC to maintain alignment with UT1, which is based on Earth's rotation. Since 1972, 27 leap seconds have been added. However, these adjustments have posed challenges for high-precision computing systems, including data centers and financial trading platforms, which rely on precise time synchronization. Disruptions have been noted in the past, such as outages affecting major websites and services when leap seconds were introduced.
Meta, for instance, has been vocal about the difficulties leap seconds present to hardware infrastructure management. Scientists have also expressed concern about the potential for even more disruptive "negative" leap seconds, which might have been required as Earth's rotation has sped up in recent years.
The new system will permit a drift of up to an hour between UTC and UT1 before intervention is required. This divergence is not expected to necessitate an adjustment for at least a millennium, simplifying timekeeping for critical digital systems. While the connection between global time and Earth's rotation will be maintained, it will be less stringent.
Dr. Setnam Shemar, a principal scientist at the National Physical Laboratory, stated that the decision balances the need for accurate timekeeping with the risks posed by leap seconds to essential systems. This change is expected to remove uncertainty for those managing time-dependent infrastructure worldwide.