Meton was a geometrician, astronomer, engineer and inventor, active during the 5th century BC in Athens. He is most widely known for discovering the Metonic cycle, a calendar system which was introduced in 432 BC and was used as the lunisolar Attic calendar.
He studied geometry and astronomy from his teacher Phaeinus, who made celestial observations from Mount Lycabettus, where he had established his own observatory. Meton’s most important discovery is the Metonic cycle or “Lunar cycle”, a lunar calendar which is composed of 19 years. Meton calculated that 19 solar years correspond to 6940 days and in turn to 235 lunar months. He also introduced the notion of the embolismic month, the 13th month that was added in certain years of the cycle. These were based on Meton’s own observations, together with his student’s Euctemon, with whom he examined the positions of the sun. The Metonic cycle was used as the basis of the Greek calendar until its replacement by the Gregorian calendar in 46. To this day, the Metonic cycle is used for the calculation of the Easter Sunday each year because every 19 years the same lunar phases are repeated.
100 years after Meton, Calippus developed the Calippic cycle, which was composed of 76 years with a mean year of 365 days. The world’s oldest astronomical computer, the Antikythera mechanism has both cycles built into it, each with its own set of cogwheels, and was able to perform astronomical calculations based on these two cycles.
Except from the development of the Metonic cycle, Meton built a solar horologeion (clock) which was placed in Pnyx, the same place where his observatory was located, ruins of which can still be seen today. Furthermore, he constructed the hydragogeion (aqueduct) of Colonus, the calendar of Athens, which was a large marble pillar with plaques of orichalcos which showed the months, the years, the holidays and the rise and dawn of the sun and the stars, made important discoveries on the equinoxes and the solstices and wrote several books, all of which were burned during the Middle Ages.
Meton was popular enough during his own lifetime to even make a cameo appearance as a character in Aristophanes’ Birds, where he comes into the stage with his topographic instruments to solve some geometrical problems. Today, a lunar crater is named after him, in his honour.