Snape & Marauders: birthdays or date starting Hogwarts

[smallbrownfrog]

I'm working on a fic that has some Marauder era stuff and I'm trying to figure out what year Snape, Lily, and the Marauders all started at Hogwarts. Do we have a definite birthday for any of the 5 so we can be sure of when they started at Hogwarts? I looked at the HP Lexicon website but different pages there are giving me different answers.

http://www.hp-lexicon.org/timelines/timeline_snape.html has Snape starting school in 1971.

http://www.hp-lexicon.org/timelines/timeline.php?startyear=1960&endyear=1998 suggests 1970.