In recent years, scientists have observed an unexpected acceleration in the Earth's rotation, potentially leading to the shortest days ever recorded. Data available up to July 2025 indicates that the shortest days were recorded on July 5, 2024, when the day was 1.66 milliseconds shorter than the 24-hour average.
The cause of this acceleration remains unclear, but some researchers suggest that melting glaciers and the redistribution of water mass could be influencing the Earth's rotation. A 2024 NASA study showed that melting glaciers and sea level changes affect the Earth's axis of rotation and the length of days.
This acceleration could have implications for systems that rely on precise time measurements, such as GPS and communication networks. Adjustments to atomic clocks have been necessary in the past to compensate for variations in Earth's rotation. If the current trend continues, it may be necessary to add or subtract a leap second to maintain global time synchronization.