A Saros is a period of 18 years 11.32 days (6585.32 days), or 223 lunations, discovered by the Babylonians, after which the Sun, the Moon and the nodes of the Moon's orbit return to virtually the same relative positions. This begins a new cycle of lunar and solar eclipses, the difference of a fraction of a day causing each eclipse to fall about 120° west of its counterpart in the previous cycle.