[1] Rata Die - Wikipedia, the free encyclopedia ( (1/6/2014, 5:53:01 PM 版)) https://en.wikipedia.org/wiki/Rata_Die
[2] Perl の DateTime が採用しています。
DateTime
[3] Date - date 3.1.2 (3/28/2019, 11:38:49 AM) https://package.elm-lang.org/packages/justinmimbs/date/latest/Date#fromRataDie
Google search: Rata Die