Did you know that a few billion years ago, earth was spinning at a much faster rate. At that time, a day was only 8 hours long.

Even today, changing ocean currents, melting ice sheets and earth quakes can minutely change the location of the "center of mass" of our planet. This in turn changes the direction of the spin axis, as well as the spin rate.

You and I won't notice these subtle changes, but they are a major issue for the engineers who send space craft to far-away places. A tiny miscalculation can make the difference between hitting the target or missing it by thousands of miles.

In the link below, the term ESA stands for European Space Agency, the equivalent of our NASA

https://phys.org/news/2021-03-track-spacecraft-earth.html