[Pippin]

W"ho besides me caught the error with Hermione's birthday?"

I did!

"In POA her birthday is in September. In this book, she takes her apparation test, which puts her birthday during the school year."

I saw that too and was wondering about that.

[Not A Snowbird]

I'm told her birthday didn't make the "cutoff", so she's a year older than Harry and half a year older than Ron.

That would explain it.