No Leap Second Planned for End of 2026

The International Earth Rotation and Reference Systems Service (IERS) has announced that a leap second will not be added at the end of December 2026. This decision reflects a recent slowing of Earth's rotation, which has pushed back the predicted need for a negative leap second.

Leap seconds are fractional adjustments made to Coordinated Universal Time (UTC) – the world's time standard – to keep it within 0.9 seconds of UT1, a time scale based on Earth's actual rotation. The IERS, established in 1987, is responsible for monitoring Earth's rotation and announcing leap second decisions.

The most recent leap second was added on December 31, 2016. However, recent research suggests that factors such as melting ice sheets are altering Earth's rotation speed. This change has shifted the timeline for the first potential negative leap second from 2026 to 2029.

While intended to keep atomic time synchronized with Earth's spin, the unpredictable nature of leap seconds has caused complications for digital systems, including navigation, communication, and financial networks. Concerns over these potential disruptions have led to discussions among international metrology experts to discontinue the use of leap seconds altogether, with a target end date of 2035.