At Christmas we celebrate the birth of Jesus, to be sure. But, as Martin Luther says:
"We see here how Christ, as it were, takes our birth from us and absorbs it in his birth, and grants us his, that in it we might become pure and holy, as if it were our own, so that every Christian may rejoice and glory in Christ’s birth as much as if we were born of Mary as was Jesus.”
So, Merry Christmas and Happy Birthday!