[Marcos Bonci]
... But I still don't understand why datetime.datetime.toordinal returns an int that truncates time information. Is this deliberate?
That it does exactly what it's documented to do is a clue about that ;-) As the module docs say, the notion of "ordinal" was deliberately defined in this way: This matches the definition of the “proleptic Gregorian” calendar in Dershowitz and Reingold’s book "Calendrical Calculations", where it’s the base calendar for all computations. See the book for algorithms for converting between proleptic Gregorian ordinals and many other calendar systems. That's the primary use case we had in mind for date & datetime ordinals. Indeed, the meaning of "ordinal" is "an integer indicating position in a sequence".