Overview

• Aug. 5 is predicted to be 1.25 milliseconds shorter than a standard day, making it the third abbreviated rotation in 2025.
• This summer’s short days follow July 9 and July 22 anomalies, marking the first year with three millisecond-scale spin-ups.
• The International Earth Rotation and Reference Systems Service and the U.S. Naval Observatory have confirmed the forecasts and noted the spin-up defies atmospheric and oceanic explanations.
• Researchers suggest deep-Earth dynamics and the moon’s maximum declination relative to the equator as probable drivers of the accelerating rotation.
• Timekeeping authorities are drafting protocols for the first-ever negative leap second to realign Coordinated Universal Time with Earth’s variable spin.