International timekeepers are considering whether to abolish the “leap second,” an extra second occasionally added to clocks to sync them with Earth’s rotation, which can cause issues for computer systems. The General Conference on Weights and Measures, meeting from October 13 to 15, 2026, will consider a proposal to make Coordinated Universal Time (UTC) a continuous scale by May 20, 2027.
The Technical Burden of Leap Seconds
Atomic clocks provide a level of precision that Earth’s rotation simply cannot match. Since 1972, humanity has added 27 leap seconds to keep civil time aligned with the planet’s irregular spin. While this keeps calendars accurate, it creates significant friction for modern computing. Many operating systems are built on the assumption that a day contains exactly 86,400 seconds, and the sudden injection of an extra second can cause massive system errors.
In 2012, for example, a leap second forced Reddit to experience a widespread system failure. Because of these risks, major tech firms like Google and Meta now employ a “smearing” technique, which spreads the additional second across a longer period to avoid the shock of an abrupt jump. These companies have lobbied heavily for a more stable, predictable timekeeping standard.
Why Earth’s Rotation Speed Is Creating Urgency
The push for reform has intensified because Earth’s rotation has been unusually fast since 2015. In 2020, scientists recorded 28 days where the planet completed a full rotation in less than 86,400 atomic seconds. The shortest day ever measured occurred on June 29, 2022, when Earth finished its spin 1.59 milliseconds early.
This acceleration presents a new, untested challenge for engineers. If the trend continues, the world may need to subtract a “negative leap second” for the first time in history. No one knows how current Linux kernels or legacy database systems would handle a day that is technically shorter than 86,400 seconds. The uncertainty surrounding this potential negative adjustment is driving the current push to move away from the traditional leap second model.
Shifting to an Hour-Based Correction
The proposal on the table in 2026 would authorize a drift of up to 3,600 seconds, or one hour, between atomic time and Earth’s rotation. This effectively replaces the frequent, small, and disruptive leap seconds with a much larger “leap hour” that would only be required every few centuries. This shift would allow UTC to remain continuous for the foreseeable future.
While this change simplifies software development, it does require a shift in how specialized users interact with time. Astronomers, geologists, and navigators who rely on the precise orientation of the Earth must account for the growing gap between UTC and UT1, the time scale tied to the planet’s rotation. Similar to how smartphones currently handle magnetic declination—the difference between magnetic and geographic north—future software would likely automate these adjustments for civilian use.
Questions About the Future of Time
- Will this change affect my smartphone’s clock?
Most consumer devices will see no visible change, as they rarely display seconds to the user. The adjustment is largely a background task for network time protocols and metrology systems. - Are leap years also being removed?
No. Leap years, which compensate for Earth’s orbit around the sun, are unaffected by this proposal. They remain essential for keeping the seasons aligned with the calendar. - When would the first “leap hour” occur?
The current proposal does not set a firm schedule for such an event. Given the current drift rate, it would likely not be necessary for several hundred years.
The General Conference on Weights and Measures, which includes over 100 member countries, has been refining these standards since adopting the cesium-133 atomic definition in 1967. If the resolution passes this October, the world will officially move toward a continuous time scale by mid-2027.
