»Yes, I changed Ginny's birthday for the purposes of the story.«
...and there you have a problem:
For Neville, Harry and Ron are born in 1980 and Ginny in 1981 (August) she would be 2 years younger in school, if she was born in October 1981. If you say, she is born in October 1980, she is only 7 month (plus some days) younger than Ron - there you have a biological problem, although, Ron said, she was early... bit tricky, but may do. In that case Hermione would be the only one, not born in 1980, instead in 1979. I'm wondering, if this will have to say something... :)
BTW: Great story so far!
"Mischief managed"
AKOM
PS: Sorry for grammar etc. - English is my 2nd foreign language.