Well if it's available in retail stores the friday before, then I would consider that the release date. It's not like someone got a pre-order early, or anything, it was available to anyone and everyone, thus "released."
Though yes, Tuesday is typically Retail Release day. I think a lot of Mixtapes "release" on Thursday or Friday though. *Shrugs* Rakim was going to pull something like this two years ago, trying to release Seventh Seal on 07/07/07, but, yeah... that didn't happen.