Calculating days between two dates in C

Oh, that was me just messing around, thinking that it might be easier to subtract five if my results were consistently five over what they're supposed to be.

I'm currently stuck on the structure part, and I'll elaborate when I get home.

Edit: You weren't wrong about that second part, either. I get 390 days between 12/31/2011 and 1/1/2012. Blah.