Work is just plain amazing sometimes....

So, thanks to an internal error here, people seem to think that this sunday is my birthday. Which would pretty much explain to me why my actual birthday (the 13th) was pretty much ignored around the office. But now I'm suddenly getting e-cards as well as physical cards from co workers. Sigh. The real question is though, should I tell them the truth about the date mix up, or just simply nod and smile?