[1] [CITE[julianday.pdf]], [TIME[2017-08-11T23:13:49.000Z]], [TIME[2023-04-21T13:08:51.681Z]] <http://fomalhautpsa.sakura.ne.jp/Science/OgawaKiyohiko/julianday.pdf#page=2>

[2] [CITE@ja[メトン周期 - Wikipedia]]
([TIME[2019-03-23 12:42:21 +09:00]])
<https://ja.wikipedia.org/wiki/%E3%83%A1%E3%83%88%E3%83%B3%E5%91%A8%E6%9C%9F#%E5%A4%AA%E9%99%BD%E5%91%A8%E6%9C%9F>

[3] [CITE@ja[orbital period | RADIO音楽生活~♪]], [TIME[2023-04-21T13:14:31.000Z]] <https://ameblo.jp/radio-duck/entry-10578852178.html>