But the dating of Christmas derives from the Jewish Hanukkah (which itself has its roots in books that are canonical for most Christians, but which have never been so for Protestants, nor for any Jews), not from the pagan Saturnalia or anything else.
Most, if not all, allegations to the contrary derive from Protestant polemic against practices originating in the Middle Ages, and usually the Late Middle Ages at that.
But the real ultra-Protestant argument, still advanced by the Free Presbyterian Church of Scotland, was and is purely and simply that nowhere in the Bible is it enjoined to celebrate the birthday of Jesus.
The Jehovah's Witnesses' argument, to which the above link refers, is founded in and on a basic factual error.
The modern religion known as Paganism is an invention from scratch, the very earliest roots of which are in the late nineteenth century. Making it no older, and at least arguably newer, than the Jehovah's Witnesses.