Molly Weasley's Faulty Memory

[uncmark]

No: HPFGUIDX 43214

Help me out if this was discussed before. I was rereading GofF and 
Molly's remebrance of her Hogwart's days (right before the third task)

Molly noticed the Whomping Willow and mentions it was planted after 
her time (which would make her older then Harry's parents). She also 
says that the Groundskeeper was Ogg. Is this different then Hagrid's 
position of Keeper of the Keys and Grounds?

Hagrid was expelled and became groundskeeper about 50 years before 
Harry's Time (placed at 1943 by the Harry Potter Lexicon) So who was 
Ogg and when did Molly and Arthur attend Hogwarts? 

Uncmark