No, Carl, because a "birthday" commemorates a birth, not a conception. Holding that life begins at conception (the scientific fact), does not require anyone to celebrate that day -- even if it were a simple thing to determine. The fact is, with some young married couples (and others, of course) sexual intercourse does happen quite often. And it used to be that it was purposeful to have children!
Anyway, even then, conception can sometimes occur a day or two after intercourse (and thus "plan B" birth control). The day of conception is usually figured backward from the first missed "period."