Butcher -- there is often a gap between the release date and when the game hits store shelves. More and more, I'm seeing varied definitions of what "release" means.
To some publishers, the game releases when it starts shipping to warehouses and online stores, and then from these intermediary stops, on to stores and online customers -- so there's a gap. Other publishers try to time their "release" announcements so that the game is actually hitting shelves at the same time as the "release date" announcements.
I wish I could hit the release date squarely on the nose each time, but I never seem to manage that.