The death and birth of the Unconquered Sun (Sol Invictus) has for millenniums been worshipped on December 21 – 25, (Winter Solstice - shortest day in the year) as the source of our energy and life on earth. December 25 as such is revered as a festive season for the birthday of the Sun God Mithra (Apollo, Marduk, Ra etc) and .if we should make belief, for Jesus Christ, the SON, as well.