How long is the precession of the equinoxes?
Apparently, equinoxes times are fixed. Actually, there is continuous shift westward due to cyclic (period 25800 years) precession-motion of spin-axis of Earth.
The cycle-period 258 centuries for the precession-motion is called Great Year. The spin-axis generates a double cone with vertex at the center of the Earth in one Great Year (also called Platonic Year). The precession rate for an equinox is nearly 20m 23s / year, nearly.