saros

   a unit of time used in astronomy, mostly in predicting solar and lunar eclipses. The saros is equal to 6585.32 days¹ (6585 days 7 hours 23 minutes), which is exactly 223 lunar months. (This is either 10.32 or 11.32 days more than 18 years, depending on the number of leap years during the period.) Astronomers in ancient times discovered that the saros is very nearly equal to 19 eclipse years (6585.78 days). This means that one saros after an eclipse the Sun, Moon, and Earth return almost exactly to the same position and another, very similar eclipse occurs. However, because of the 7 hours 23 minutes included, the Earth has turned about one third of a revolution and the new eclipse occurs about 116° of longitude west of the preceding one. After 3 saros, the eclipse returns nearly to its original location. Thus eclipses at a particular location tend to repeat with a period of 3 saros or 54 years and about 1 month. Thus the last total solar eclipse in North Carolina, on 1970 March 7, will repeat on 2024 April 8 and again on 2078 May 11.