datetime review part 2 [Update 6]

[Jonathan M Davis]

Newest: http://is.gd/hsNcq

Since, I just overhauled some of my unit test functions, it seems appropriate to 
repost the changes. So, here they are. I also changed the days of the week to 
their abbreviated names, which I had meant to do earlier but forgot. No changes 
to the API other than the days of the week.

- Jonathan M Davis


P.S. Remember to link with advapi32.lib on Windows.