Message 63446 - Python tracker

The datetime.datetime class overrides some arithmetic operations for it
to be able to add or subtract timedeltas. However, the result of A + B
operation, where A is instance of a subclass of datetime and B is
timedelta instance will be always the instance of base datetime.

This is extremely annoying and requires to override arithmetic operators
and writing a lots of rubbish to replace the datetime base object with
type(self)