m-parry reported the issue #29921 "datetime validation is stricter in 3.6.1 than previous versions". He is right, the C API of Python 3.6.1 is now stricter than Python 2.7 and 3.5. The C API doesn't allow anymore to create datetime objects outside the [datetime.datetime.min; datetime.datetime.max] range (what I would call "invalid" datetime objects). I closed the bug as NOT A BUG since I consider that it's a deliberate design choice and not a regression.