a period of 19 years (235 lunar months), after which the new and full moons return to the same day of the year. It was the basis of the ancient Greek calendar, and is still used for calculating movable feasts such as Easter.
Origin:
named after Metōn, an Athenian astronomer of the 5th century bc
Metonic cycle in other Oxford dictionaries
Definition of Metonic cycle in the US English dictionary
