Doc nit: "When ``%z`` directive" -> "When the ``%z`` directive"
The _strptime._strptime docstring is inaccurate: it claim to return a time struct, but actually returns tuple, int; please could you also add docstrings for _strptime_time and _strptime_datetime?
Spacing in datetimemodule.c: "if( module == NULL)" -> "if (module == NULL)". Also, is there any particular reason for initializing 'result' to NULL? (Or even for using result at all; you could just do "return PyObject_CallMethod(... ").
I'm mildly distressed by the inability of strptime to parse UTC offsets in the +HH:MM form that str(timezone) produces, but I'm not sure what the solution to that is.
Otherwise, this all looks good to my non-expert eye.