I'm attaching a patch for Lib/_strptime.py that handles the month differently in __calc_date_time. It cycles all months, trying to find one where the full and abbrev names are different and matches it against the timestamp created by strftime. 

This solution is a hack, but so is the whole __calc_date_time function :-) [IMHO]

All tests pass and I also tried it manually with all the problematic locales reported by Alexander - seems to work correctly.

If this looks OK to you guys I can commit and backport.