Scientists Consider Replacing Leap Seconds with a Century-Scale 'Extra Hour' to Protect Global Digital Infrastructure from Negative Leap Second Risks

Global timekeeping authorities are preparing a landmark decision that could fundamentally change how the world manages civil time. Instead of continuing to insert occasional leap seconds, they are considering a system that would allow an extra hour to accumulate over hundreds of years before any major correction is needed. The goal is not to lengthen the day but to permanently remove the recurring one-second adjustments that have long destabilized computer systems and may become even more dangerous as Earth's rotation speeds up.

The leap second was first introduced in 1972 to keep Coordinated Universal Time (UTC) aligned with the planet's irregular rotation. While atomic clocks maintain exceptional stability, Earth's spin varies due to internal geological processes, ocean currents, atmospheric conditions, and other factors. When the difference between atomic time and astronomical time grows too large, specialists add a single extra second to the calendar year.

For ordinary users the adjustment is barely noticeable. For digital infrastructure, however, it creates serious problems. Computer systems rely on precise sequencing of events, and an abruptly inserted second has already triggered outages at Meta, Reddit, and Cloudflare. It has also disrupted airline operations and interfered with high-frequency stock trading. As networks and financial platforms operate at ever-higher speeds, their tolerance for non-standard time changes continues to shrink.

Many developers have therefore adopted a workaround known as leap-second smearing, in which the extra second is gradually distributed over a longer interval rather than inserted all at once. While this approach reduces immediate crashes, it creates a new inconsistency: different systems begin operating under slightly different time rules.

No leap seconds have been added since 2016 because Earth's rotation has begun to accelerate. Scientists are now discussing the opposite scenario: if the planet starts to outpace atomic time, the first-ever negative leap second may be required. Removing a second from UTC has never been attempted, and experts have no data on how today's infrastructure would respond.

The risk of a negative leap second prompted the General Conference on Weights and Measures in 2022 to accelerate a review of UTC rules, originally targeting 2035 as the deadline. Updated assessments now indicate that waiting that long could be risky, with the probability of needing a negative leap second before 2035 estimated at approximately 30 percent.

The new proposal under discussion would replace the current one-second corrections with a much larger allowable deviation—potentially an entire hour—between atomic time and Earth's position. This change would push the next major adjustment centuries into the future, effectively ending the era of leap seconds for practical purposes. If approved, the revised rules could come into force as early as 2027.

The International Bureau of Weights and Measures considers the issue urgent. Even a 10 percent chance of a negative leap second is viewed as unacceptable for global digital systems. By removing the most disruptive element before it can trigger unpredictable large-scale failures, authorities hope to safeguard servers, exchanges, aviation networks, and telecommunications infrastructure.

The reform would not completely sever the connection between civil time and Earth's rotation, but it would make that link far more flexible. UTC would continue to rely primarily on atomic clocks, while any accumulated difference with astronomical time would be allowed to grow over decades or centuries. Although humanity may eventually have to address an entire hour of divergence, computer systems would no longer need to prepare for sudden one-second jumps that cause more damage than they appear to.