We don't the article was incorrect. --JKoch(Owl Me!) 02:05, December 14, 2010 (UTC)
On the timeline, 1971 is missing. On September 1st in 1971, Severus Snape, Lily Evans and the Marauders started their Hogwarts career and were Sorted into Gryffindor (except Snape, obviously, who was placed in Slytherin).