METONIC CYCLE, in chronology, a period of 19 years during which there are 235 lunations, so called because discovered by Melon. Computation from modern data shows that 235 lunations are 6939 days, 16-5 hours; and 19 solar years, 6939 days, 14-5 hours. The relation between integral numbers of months and years expressed by Melon's rule therefore deviates only two hours from the truth. Since 19 Julian years make 6939 days, 1 8 hours, the relation errs by only 1-5 hour when the Julian year is taken. Meton was an Athenian astronomer (fl. 432 B.C.).
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)