Billie(main singer) his father died on September 1 ,1982 because of cancer,and at his dad's funeral Billie cried and ran home and locked himself in his room,when his mom came home she knocked on his door and Billie simply said "wake me up when september ends" hence the title of the song. His dad died when he was 10, Billie wrote the song seven years after his dad died hence the line " seven years has gone so fast". Later in the song, he says "twenty years has gone so fast". 10 plus 7 plus 20 is thirty-seven, which was Billie's age at that time. It would also make sense that he wishes he could sleep through September, because perhaps he is reminded of his father in september.