Leap seconds

A leap second is an occasional one-second adjustment added to Coordinated Universal Time (UTC) to keep clocks aligned with Earth's slightly unpredictable rotation. Because Earth's rotation can slow down or speed up due to gravitational forces and other factors, our standard time isn't perfectly synchronized with Earth's actual position. When needed, a leap second is inserted—usually on June 30 or December 31—to ensure our clocks stay accurate relative to the planet's rotation. This adjustment helps maintain consistent timekeeping for navigation, satellite operations, and scientific purposes.