[1] Rata Die - Wikipedia, the free encyclopedia ( (2014-01-07 02:53:01 +09:00 版)) https://en.wikipedia.org/wiki/Rata_Die

[2] Perl の DateTime が採用しています。

[3] Date - date 3.1.2 (2019-03-28 20:38:49 +09:00) https://package.elm-lang.org/packages/justinmimbs/date/latest/Date#fromRataDie