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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 as a method of calculating dates. Meton found that 19 solar years are almost equal to 235 lunar months — nearly 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 on June 27, 432 BCE, New Year's Day for the Athenians. But the actual summer solstice began on 28 June, 432 BCE, when the Sun was 90 degrees ahead of the vernal equinox. It is therefore not correct to associate 27 June, 432 BCE with any solstice. Meton may have used some measure of trepidation and thus his True Sun might have had a value different from what we compute from the modern formula. Many ancient astronomers, from Babylonians, Indians, Arabs to Copernicus used trepidation which is now believed to be erroneous. But trepidation (pendulum-like oscillation of the equinox) must be taken into account for getting correct dates in ancient history, because many ancients used it. Maximum value of trepidation was + or - 8° in Europe and + or - 27° in India. Most traditional Indian almanacs still use it. There is a possibility that the Metonic New Year was associated with some ancient practice which modern scholars do not take into consideration.

Meton appears briefly as a character in Aristophanes' play The Birds. He comes onstage carrying surveying instruments and is described as a geometer.

None of his works survive.

• Toomer, G. J. "Meton." Dictionary of Scientific Biography 9:337-40.
• Pannekoek, A. "Planetary Theories - the Planetary Theory of Kidinnu." Popular Astronomy 55, 10/1947, p 422

• Meton of Athens
• Greek Astronomy