Having estimated the length of a day over the past 3000 years, astronomers have shown that they lengthen by 2 milliseconds over a century.
Leslie Morrison and his colleagues at the University of Durham and the Marine Astronomical Yearbook have collected and summarized a huge body of historical data on the rotation of the Earth since 780 BC. e. and until 2015. In an article published by the journal Proceedings of the Royal Society A, they note that accurate measurements of the length of the day began with the introduction of International Atomic Time in 1962, and before that they relied on data from astronomy, archeology, geophysics and just historical evidence.
The theoretical calculations of the time of the past lunar and solar eclipses were compared with the chronicles - ancient Chinese, Babylonian, Greek, Egyptian, medieval … lengthened by about 2ms.
The deceleration of rotation is faster than if it was caused by only one internal friction arising from the tidal forces and the moon. According to scientists, an additional contribution to it is made by the global redistribution of masses, which has been going on since the last ice age, including the melting of polar ice and changes in sea level. Complex, poorly understood electromagnetic interactions between the core and mantle of a planet, as well as earthquakes, can also have a certain effect on rotation.
Sergey Vasiliev