This question has come up before so here's the definitive answer from Awake!, the purpose of which is to clear up any ambiguity on the matter:
Awake-2004-7-8-p.-30:
Piñatas I read with interest the article "The Piñata—An Ancient Tradition." (September 22, 2003) It left me with some questions. The ties to false religion are well-documented. But the article seemed to take the position that as long as it doesn’t bother someone’s conscience, it is OK. What about birthdays and holidays such as Christmas? S. W., United States
"Awake!" responds: Christians refrain from any celebrations or customs that continue to involve false religious beliefs or activities that violate Bible principles. For example, the Bible definitely puts birthday celebrations in a bad light. (Genesis 40:20; Matthew 14:6-10) However, if it is very obvious that a custom has no current false religious significance and involves no violation of Bible principles, each Christian must make a personal decision as to whether he will follow such a custom.
Right. So that clears it up perfectly. The "Bible definitely puts birthday celebrations in a bad light" and "each Christian must make a personal decision". So, to answer the question, err.... em, well I can't. It's impossible to tell from the above paragraph (which was written for the sole purpose of clarifying the matter) what the answer is. That sort of doublespeak can't happen accidentally. It takes a deliberate effort of will to craft an answer to a question that doesn't really answer the question. Watchtower publications seem to do this more and more lately.
