Mistakes happen to everyone..

The mistakes committed by Rowling while writing her book...


*Every year, students board the Hogwarts Express on September 1, and
the next day when their classes start, it's always a Monday. How can
September 2 be a Monday EVERY year?

*In Book 1: US, paperback edition, pg. 96. It says that Percy had a
silver prefects' badge. Book 5: US, hard-cover edition, pg. 161.
Here it says that the prefects' badges are scarlet and gold.

*At the second to last page of the Scholastic Paperback version
of "Harry Potter and the Chamber of Secrets", it says a bit about
the third book, Harry Potter and the Prisoner of Azkaban. " Harry
Potter has to sneak back to his third year at Hogwarts after
accidentally inflating his horrible Aunt Petunia". But how could
that be. As we all know that Harry inflated his horrible Aunt
Marge.

*Dumbledore was Transfiguration teacher before he was Headmaster, and
Remus Lupin was born in/around 1960 (in OotP Snape is 35 or 36, so
we can make an estimate on Remus' age in PoA from that). Now: On
page 352 of the hardback (Ch. Moony, Wormtail, Padfoot, and Prongs),
Lupin says "I was a very small boy when I received the [werewolf]
bite," and on the next page says "It seemed impossible that I would
be able to come to Hogwarts . . . But then Dumbledore became
Headmaster . . . " and of course Dumbledore allowed Remus to attend
Hogwarts. Now skip ahead to OotP. On page 321 (Ch. The Hogwarts High
Inquisitor), McGonagall says she has been teaching at Hogwarts
for "thirty-nine years this December." Assuming that McGonagall has
always taught Transfiguration (never any other subject) at Hogwarts,
and also assuming that at this point Remus would also be 35 or 36
(based on Snape's age), then Dumbledore would have been Headmaster
for at least three years before Remus was born. So why did Remus say
he wouldn't have been able to attend Hogwarts if Dumbledore hadn't
become Headmaster after Remus was bitten?