Meton of Athens in Wikipedia

Meton of Athens (Greek: Μέτων ὁ Ἀθηναῖος) was a Greek mathematician, astronomer, geometer, and engineer who lived in Athens in the 5th century BCE. He is best known for the 19-year Metonic cycle which he introduced in 432 BCE into the lunisolar Attic calendar. Meton found that 19 solar years are almost equal to 235 lunar months, both totalling 6940 days. Meton was one of the first Greek astronomers to make accurate astronomical observations. It is widely believed that, working with Euctemon, he observed the summer solstice, which marked the Athenian New Year, in 432 BCE. The Metonic cycle appears in the oldest known astronomical device, the Antikythera Mechanism (2nd century BCE) together with its multiple the Callippus cycle of 76 years. The foundations of Meton's observatory in Athens are still visible just behind the podium of the Pnyx, the ancient parliament. Meton found the dates of equinoxes and solstices by observing sunrise from his observatory. The bisectrice[clarification needed] of the observatory lies in an easterly direction, between the Acropolis and the Lycabetus hill. Meton appears briefly as a character in Aristophanes' play The Birds (414 BCE). He comes on stage carrying surveying instruments and is described as a geometer. Another Greek astronomer, Callippus, continued the work of Meton and discovered that using a multiple of Meton's cycle, Callippus cycle, equal to 76 years the predictions are more accurate[clarification needed]. None of Meton's works survive.