Time will tell I suppose. I'll be putting my money on a 18:00 GMT unlock. But if you are right I won't complain. Getting the game earlier than expected is always a nice touch.
If you read my earlier posts, you'll see I actually said Paradox games, without exception as far as I know, have all appeared to release in the evening (ie, 1800GMT/1900 BST).
It is why I asked you to clarify if you meant ALL Steam games or Paradox ones. As I also said, it entirely depends on when the developer wants to release it, with times varying wildly - examples provided.