This is something that I have learned to loathe about WTBS, they pick and choose their secular evidence to suit them:
The ancient Anglo-Saxons celebrated the birthday of the "Lord Moon", spoken of as meni at Isaiah 65:11 (margin), by making cakes "called Nur-Cakes, or Birthcakes"
There is also evidence to support the fact that the birthday cake is merely a reproduction of the placenta. In older cultures, where women had much more traditional means of dealing with the cycles of life (eg, even in Israelite tribes they had the red tent where women would retire to for their menstruation time) they would actually honour and respect life's conditions. This wasn't veneration, just their way of being in tune with life and celebrating life. They did things differently back then because of their limitations. Today, the WTBS would write an article on "Jehovah's marvelous life giving creation - the placenta", or a pregnant women would spend time reading about the miracles of life, the baby's growth stages, the job of the placenta etc and be in awe and gratitude for it. Back in older times they expressed it in a different way, not with written word, books or the internet, they did it the only way they knew how, by marking occasions, passing down wisdom from generation to generation - in song, stories and celebrations.
No doubt the Anglo-Saxons also had their own reasons for doing what they did. But for every 'pagan' example they can come up with, there are also other examples that aren't pagan, just cultural or traditional.
Shit, this birthday one bugs me because it is such a meaninglessly obtuse rule they have. It goes against the whole spirit of valuing the gift of life.
Again, even though it has been said. The whole aspect around marriage (celebrating anniversaries, which in my mind is celebrating the 'birth' of a marriage. And the rings, which can be argued, have pagan origins) is proof that they just pick and choose what suits them.