[1] January 0 - Wikipedia (2017-01-05 18:35:14 +09:00) https://en.wikipedia.org/wiki/January_0

[2] 1月0日 - Wikipedia (2018-02-19 13:04:43 +09:00) https://ja.wikipedia.org/wiki/1%E6%9C%880%E6%97%A5