[Anthony Baxter]
Erm - this particular fix was a bug fix. I'm deeply uncomfortable about adding the C version of datetime to 2.3 at this very late stage of 2.3's life cycle.
It's quite arguably a bugfix, since datetime.h in 2.3.4 exposes things that can't possibly be used outside of datetimemodule.c (the datetime type objects are referenced in the header, but not exported in a usable way). Anthony Tuininga's patch to *finish* (not really add) the datetime C API is a low-risk change regardless: it doesn't change any existing functionality, it just finishes the job of exposing it to C coders, and adds some new macros for convenience. Now if some platform header file has macros with names like PyDateTime_FromTimestamp or PyDelta_FromDSU then adding these macros to datetime.h could cause new problems. But platform header files don't have macros with names like those (if they did, we would have bumped into it while developing 2.4).