Patch from Brett Cannon:
First, the 'y' directive now handles [00, 68] as a suffix for the
21st century while [69, 99] is treated as the suffix for the 20th
century (this is for Open Group compatibility).
strptime now returns default values that make it a valid date ...
the ability to pass in a regex object to use instead of a format
string (and the inverse ability to have strptime return a regex object)
has been removed. This is in preparation for a future patch that will
add some caching internally to get a speed boost.
because it added it to 12 PM too. 12 PM should be hour 12 not hour
24.
Also cleaned up a minor style nit. There are more style problems in
this file that I'll clean up next (but I didn't want them to overwhelm
the substance of this fix).