[1] January 0 - Wikipedia (1/5/2017, 9:35:14 AM) <https://en.wikipedia.org/wiki/January_0>

[2] 1月0日 - Wikipedia (2/19/2018, 4:04:43 AM) <https://ja.wikipedia.org/wiki/1%E6%9C%880%E6%97%A5>