Seems it is playable at 9.oclock if you ordered it via Steam :
The actual launch times on PC differ by storefront. Through Uplay, Assassin’s Creed Origins will be playable at 00.01 local time (just after midnight), on 27 October. Those regions which pass midnight first will be able to play the game first. Over on Steam, it will be released at the set time of 04.00 UTC, 27 October. That means it’ll be out on Steam at 21.00 PST the day before (26 October), and at midnight in the EST zone, and so on.