This is the interval between two similar eclipses (every 223 lunar months or 6,58532 days) when the relative angles between the Sun, Moon and Moon`s nodes repeat to within a degree
This cycle predicts the occurrence of eclipses, as after a period of 18 years and 11.3 days the Earth, Moon and Sun all line up in the formation necessary to generate this celestial event.
A period of 18 years 11.3 days in which eclipses repeat themselves.