The Bureau International des Poids et Mesures (BIPM), the international body responsible for the UTC time standard, has reached a resolution to cease the practice of inserting leap seconds. This change is scheduled to take effect on May 20, 2027, and will remain in place for the foreseeable future. The decision addresses a long-standing tension between atomic time—which is highly stable—and solar time, which fluctuates due to the Earth's slowing rotation. By stopping the insertion of leap seconds, UTC will gradually drift away from Universal Time (UT1), the time scale based on the Earth's rotation.
Several technical and practical factors drove this decision. Commenters on Hacker News noted that leap seconds are a frequent source of software bugs, particularly in systems that cannot easily receive real-time updates, such as certain Internet of Things (IoT) devices. Furthermore, while leap seconds have historically been added to keep UTC in sync with the sun, 'negative' leap seconds (removing a second) have never occurred. Because many software systems have never been tested against a negative leap second, the BIPM opted to prioritize system stability over astronomical precision. The resolution suggests that the current 27 leap seconds added since the inception of the practice will be the final ones ever added.
To manage the eventual discrepancy between UTC and solar time, the BIPM proposed a 'leap hour' as a distant contingency. However, this mechanism is expected to be unnecessary for at least 1,000 years. Discussion on Hacker News highlighted a trade-off: while this move simplifies software engineering by removing the need to handle rare second adjustments, it requires systems to eventually tolerate a larger drift from solar time. Some observers pointed out that while this 'kicks the can' into the distance, it effectively decouples human-centric clock time from the Earth's rotation, potentially moving toward a future where time is treated as an independent count of seconds rather than a reflection of planetary movement.