I had a long debate with a JW elder about cebrating bithdays and his retort was scripted of corse right out of the WT.
He stated that it says in the bible that true followers should admonished in participating in the traditions of men and since most birthday celebrations were conducted toward kings or gods that correlates to us today to not celebrate birthdays including Christmas. Birthdays and the celebration of, are in other words are associated with paganism.
My position was well people today are celebrating the birthday of not a god or king, they are celebrated toward people as a expression of love and respect to these ones, in spite that celebrating birthdays may have originated by other means and practice.