0
Pyth, 30 * 75% = 22.5 bytes
I'm 100% positive that this could be made shorter, but hey, it's my first Pyth program! \o/
+-28%+-+-Q2/Q4/Q100/Q400 7"-11
Test suite
Outputs the date in dd-mm format.
Please suggest ways to golf this if you can! I'd like to learn more about Pyth.