> I've encountered an issue on anaconda python on windows 10 v1909 which I suspect is related. It looks like no dates in 1970 can be converted to datetime.timestamp():

Yeah... there is more related weirdness going on.

>>> datetime(1970, 1, 3).astimezone(timezone.utc)
datetime.datetime(1970, 1, 2, 16, 0, tzinfo=datetime.timezone.utc)
>>> datetime(1970, 1, 2).astimezone(timezone.utc)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: [Errno 22] Invalid argument
>>> datetime(1970, 1, 1, 16, 0, tzinfo=timezone.utc)
datetime.datetime(1970, 1, 1, 16, 0, tzinfo=datetime.timezone.utc)