1 article for "Greek Calendar"

Early Greek calendarial reckoning was rather chaotic. Each community had a separate calendar. All Greek calendars were lunar until the Roman period, and kept roughly in a fixed relation to the seasons by the intercalation of a 13th month when required; but the intercalations were determined by local public authorities, and were different in different calendars in addition to being irregular. There was also great variety in the season when the year began in different calendars. From the 6th century BC onwards, a number of cycles were successively devised by the Greek astronomers as a basis for regulating the lunar calendar by fixed rules instead of by arbitrary intercalation. Among these, the Metonic and Callippic cycles came to be used by astronomers for dating observations, and appear to have been used over a period of several centuries extending into the Middle Ages to establish the dates of New Moon for purposes of religious calendars. In the Metonic cycle, 19 years were equated to 235 months and to 6940 days; in the Callippic cycle, 76 years were equated to 940 lunations and to 27759 days, one day less than 4 Metonic cycles.

See also:
♦ Metonic Cycle ♦ Callippic Cycle