Pokemon.com has announced that sets will now be legal on the third Friday of the same month the set is released. Since Sun & Moon will be released on Friday, February 3rd, this means the set will be legal on Friday, February 17th.
Promo cards will now be legal on the first or third Friday of the month after the product is released. This will make it much easier to determine when promos are legal for tournament play since product release dates are always confusing. So since the Snorlax GX Box will be released in December, this means Snorlax GX will be legal on Friday, January 6th.