IERS confirms no leap second for December 2026 — UTC stays put

The International Earth Rotation and Reference Systems Service (IERS) has issued Bulletin C confirming that no leap second will be added at the end of December 2026. UTC will therefore remain unchanged, with no adjustment inserted at the June or December decision points that IERS uses to keep civil time aligned with Earth’s rotation. This continues a multi-year stretch without a positive leap second, the last of which was applied at the end of 2016.

Leap seconds exist to reconcile atomic time (TAI) with UT1, the timescale derived from the planet’s actual rotation, keeping the two within 0.9 seconds of each other. IERS monitors long-term rotation trends and announces each decision roughly six months ahead so that timekeeping infrastructure can prepare. The quiet bulletin reflects the current state of Earth’s spin, which has recently been running slightly fast rather than slow.

For engineers, a no-op bulletin is welcome news: leap seconds have historically triggered outages and kernel bugs across distributed systems, databases, and network time infrastructure whenever a 61-second minute has to be handled. The broader backdrop is that the international metrology community has voted to phase out leap seconds by 2035, after which UTC will be allowed to drift further from astronomical time — making announcements like this one increasingly routine in the interim.