Witcher 3 - Hearts of Stone Review @ IGN

Originally Posted by DArtagnan
Approximately 8 hours - which would make it the 13th in some countries, including mine.

That would be the same way they did it with the release of the full game. Pick one country to release it at midnight and release it to the world at that same moment no matter what time zone you are in.

I might just wait an extra day anyways to see if there's any major issues to be aware of.