That's not what the docs say.  E.g.: https://docs.python.org/3/reference/datamodel.html#object.__hash__ says

    By default, the __hash__() values of str, bytes and datetime objects are “salted” with an unpredictable random value. Although they remain constant within an individual Python process, they are not predictable between repeated invocations of Python.

Morever, this command really prints changing numbers:

~/svn/python/3.7-debug/python -c "import datetime;print(hash(d                      atetime.datetime(2016,10,10,0,0,0,0)))"