Metōn (English spelling) Meton

Japanese: Metōn（英語表記）Meton

…However, over time, the calendar was gradually improved, and around the 5th century BCE, a method was devised to include seven leap months in a 19-year cycle. This 19-year cycle was proposed by the Greek astronomer Meton in 432 BCE, who also used the lunisolar calendar, and was called the Metonic cycle. In China, this is called the Zhang Fa. …

From the Metonic Cycle

…a cycle of 19 calendar years divided into 235 calendar months, or 6,940 days. It was proposed by the Greek scientist Meton in 433 BCE to correct an error in the lunisolar calendar then in use. It has 12 normal years of 12 months each and 7 leap years of 13 months each. …

*Some of the terminology explanations that mention "Metōn" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…しかし時代の経過とともに暦はしだいに改良され，前5世紀ころには19年間に7個の閏月を置く方法が考案された。この19年の周期は，やはり太陰太陽暦を使用していたギリシアにおいて，前432年に天文学者メトンMetōnが提唱しメトン周期と呼ばれた。中国ではこれを章法と呼んでいる。…