Metonic cycle
/mɪˈtɒnɪk/noun
- 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.默冬周, 默东章（19年［235个阴历月］的周期, 此周期后, 新月和满月重归同一天; 是古希腊纪年法的基础, 仍用于确定复活节等变动性节日）。
词源
named after Metōn, an Athenian astronomer of the 5th cent. BC.