Assuming that you pre-ordered from the PlayStation Store, you can begin downloading Horizon: Zero Dawn in North America right now. The game, which weighs in at almost 50GB, is available for pre-load – though due to the later release date in Europe, you'll need to wait a little longer to pull the files down in the Old World.
Once the game's downloaded and installed, you'll be greeted by a timer counting down to the moment that you can play. The same applies to the game's pre-order bonus theme and art book. The good news is that there's not long to go now: Guerrilla Games' excellent open world role-playing game launches in a matter of days.