Saros

Saros, in Babylonian numeration, the number 3600, i.e.  60 times 60. In astronomy and chronology, a remarkable period of 18 years and 10 or 11 days, at the end of which every eclipse of the sun or moon recurs with little change as regards the time and the character of the eclipse. It is supposed to have afforded in ancient times the principal method of predicting eclipses (see Eclipse).