The Lyapunov time of a dynamical system is the timescale over which it is chaotic. An example of such a system in astronomy is a system of orbiting bodies, such as the Earth and the Moon. The Lyapunov exponent is its inverse.
Some calculated examples:
|solar system||50 million years|
|Pluto's orbit||20 million years|
|Kepler 36 (star system)||3000 days|