And indeed that's Python's calendar:

'A date object represents a date (year, month and day) in an idealized calendar, the current Gregorian calendar indefinitely extended in both directions.'

'This matches the definition of the “proleptic Gregorian” calendar in Dershowitz and Reingold’s book Calendrical Calculations.'

https://docs.python.org/3/library/datetime.html#id2 https://docs.python.org/3/library/datetime.html#id5

Whereas Ruby has proleptic Gregorian Time, but civic DateTime:

https://ruby-doc.org/stdlib-2.6.1/libdoc/date/rdoc/DateTime....