Through July and August of 2025, slight fluctuations in Earth’s rotation mean many of the days have been or will be measurably (though not conspicuously) shorter. On July 10, the shortest of 2025 so far, Earth completed its daily spin 1.38 milliseconds faster than usual, per data from the International Earth Rotation and Reference Systems Service (IERS). The variation is all part of a trend in recent years where Earth’s rotation is speeding up. Then, there’s the movement of Earth’s core, which is countering that longest-term trend on the scale of decades. As the core movement slows, that lost speed must be picked up by another part of the system.