Question

It said Pokemon sun and moon came out on 12/31/16 fom a gamestop book is that correct ?

Comments

Official statements from Nintendo and the Pokemon Company say that they will be released in "holiday 2016". Retailers like Gamestop might have further knowledge regarding this, but we don't know for sure; that date may or may not be accurate. At this early stage, a specific date may not exist.
Personally, I doubt that's the real date, because a December 31 release would be stupid from a business perspective. A release before Christmas is always optimal and is probably what you can expect from these games.

Answer 1

Yes, it is kind of correct, Pokemon Sun and Moon will be coming out sometime in December of 2016, however the official release date has not been announced yet. (As far as I know.)

Sources: Knowledge and this preorder page on Amazon.

Answer 2

It is a widely used placeholder date for the big Christmas titles across the industry. It will most likely be changed to an earlier date, as early as Black Friday, as we get more information closer to the release.