iTunes always puts their new releases at 11pm the day before. It's happened with every album, every single, I've stayed up to buy. UNLESS they do some weird evening release on iTunes.
But wouldn't these sales coun't for this week's billboard chart?
Sis, you guys EVERY SINGLE AND ALBUM EVER GETS RELEASED AN HOUR EARLY ON ITUNES.
It's when they update the Store. Don't worry. It's never ruined any single's performance, it won't ruin Britney's.