Page "Nutation" Paragraph 16

Because the dynamic motions of the planets are so well known, their nutations can be calculated to within arcseconds over periods of many decades.

There is another disturbance of the Earth's rotation called polar motion that can be estimated for only a few months into the future because it is influenced by rapidly and unpredictably varying things such as ocean currents, wind systems, and motions in the liquid nickel-iron outer core of the Earth.