Meton

(c. 432 bc) Greek astronomer

Nothing is known about the life and personality of Meton. His proposed cycle, called the Metonic cycle, which was not accepted by the citizens of Athens, was designed to bring the lunar month and the solar year into some form of acceptable agreement. As the lunar month is about 29½ days and the solar year is 3651/4 days there is no way a whole number of months can make up a year. An early solution to the problem was theoctaeteris, in which three intercalary (inserted) months are added to each eight-year cycle. This would lead to an error of alignment of a day and a half each eight years. Meton's suggestion was an improvement on this. He realized that 235 lunar months and 19 solar years are both 6939 days. To bring the two cycles into phase would need 7 intercalary months spread over the 19 years of the full cycle. This would produce a solar year only 30 minutes too long. The Metonic cycle was eventually adopted by the Greeks and was used until the introduction of the Julian calendar in 46 bc. The Jewish calendar still uses it.