Although the campaign mode of Halo Infinite has no official early access, you can actually try it out between 9 to 15 hours earlier if you use the New Zealand region on your console.
Well, here is the exact Halo Infinite release time in each major region of the world as well as some additional info.
Halo Infinite supports Xbox Play Anywhere feature, which means if you buy it on Xbox, you can play it for free on PC through the Xbox App.
Halo Infinite will be available on December 8 at 10 am PT/1 pm ET/6 pm UTC/7 pm BST/8 pm CEST.