It’s interesting that it works that way in 2003, so something must have changed since then. You are correct that the status date in 2010 and I believe in 2007 is set to 8am. I don’t know why but it is now a feature…:-)
This is an issue/problem/bug. I have not fully investigated the behaviour, which is not present in 2007, but to be 100% confindent you need to put “3/5/12 5pm” as the status date (including the time). Sometimes it seems to do OK without the time, but as I said, I haven’t fully investigated.