While we do not know the exact date that Christ was born, we do know why the early Christian church chose to celebrate Christmas on December 25. The church was not Christianizing a pagan festival, but was establishing the celebration of the birth of Christ as a rival celebration. Today the world has all but forgotten about the pagan gods of Rome. But at least a billion people today consider themselves to be followers of Jesus Christ and celebrate that reality every Christmas. If Jesus is not the Christ of your life, celebrating the birth of an obscure Jewish carpenter's son is ultimately meaningless.
H stands for history.
That God cloaked himself in human flesh is a verifiable historical fact. While many still debate the meaning of Christ's life, few question its historicity. R stands for rejoice. Christmas songs demonstrate that rejoicing has always been the focal point of Christmas. We rejoice not for earthly vanities, but for eternal verities.