National Time Service Center

An approximately 70-year core-related modulation of Earth rotation and its implications for the leap second

Recent observations of Universal Time (UT1) indicate an acceleration in Earth’s rotation. If sustained under the current leap-second framework, this behavior could eventually prompt consideration of a negative leap second. We examine whether the recent acceleration is consistent...

High-Precision UT1 Prediction with Different Angular Momentum Combination Schemes

Universal Time (UT1) is a core component of the Earth orientation parameters (EOP). High-precision UT1 predictions are essential for satellite navigation, deep-space exploration, and the maintenance of national standard time. Although effective angular momentum (EAM) information...