What year did the Marauders graduate from Hogwarts School of Witchcraft and Wizardry?

James Potter, Sirius Black, Remus Lupin, Peter Pettigrew, Lily Evans and their classmates. What year did they graduate?

I'm pretty sure an actual year is never mentioned...

Harry Potter was born in 1980. So probably 1978-7-9. Check on magnet. they know everything

James Potter was born c. 1957 in Britain. He is described as having hazel eyes, a slightly longer nose than Harry's, but otherwise the same thin face, same hands, same untidy black hair sticking up at the back, and (nearly) the same height as Harry during their school days. He attended Hogwarts c. 1970 to c. 1977 where he was in Gryffindor and his best friends were Sirius Black, Remus Lupin and Peter Pettigrew, the four of them being known as The Marauders. Sirius fell out with his own parents when he was around sixteen and ran away to move in with James and his parents until leaving school. He often visited the Potters, who regarded him as a "second son."

Around 1977/1978. James was born 1957 so as any mortal who goes to school, he must have finished around that time.

the book doesn't say the date even harry was born or how old was Harry's dad when he died.