Trends and variations in the irregularities of the Earth's rotation

The paper presents results of modeling various variations of the Universal Time (UT1). To develop a variation models, UT1 observations from 1901 to 2020 published by the International Earth Rotation and Reference Systems Service (IERS) were used. Using the developed method, the main variations are identified from the diverse spectrum of irregularities in the Earth's rotation, the models of which are presented as a superposition of a limited number of harmonic components. The results obtained in this paper are important for improving the accuracy of predictions of Universal Time.