Too Far Back in time

Hermione travels to the past using a time turner with Harry, they end up traveling to in hopes to help save Buckbeak and Sirius, but they end up in the past of the marauders era. Due to traveling back in time, Hermione and Harry age up 4 years. Severus and Lily are head boy and head girl. Eventual Hermione/Severus (There is mild humor, but it's in the background)