Originally posted by animal_PLANET:

Shouldnt all zones be listed as the 17th though? So some regions will have it sooner than others, but should all list as 17th. That was my logic.

Midnight September 17th (using that guess because it's the best I have and it makes no difference anyway) CEST is the exact same moment everywhere, it's just clocks will show different times. Steam store localizes currency, so why not timezone too.

Originally posted by Diabetus Maximus:

Weird though, in my library it says release date is on the 16th of September, but on the game's shop page in Steam it says on the 17th.

Yeah, that is weird. Goes against my theory about store localizing timezones, and against what the OP says.