Merry Christmas! And the question is, if Jesus was born sometime in the spring (when the shepherds were in the fields with the sheep, and the animals’ area with the manger under the house kataluma wasn’t being used), why did Christians create a winter solstice celebration for him instead?
The answer is that Paul caused it. Paul’s intent was to create a Judaism-based religion that would be universally acceptable; he was a Roman citizen, not just a member of a conquered nation, and he wanted his religion to be Roman as well as Jewish. Reputedly epileptic, his seizures gave rise to religious visions, the most famous being of Jesus (who he never met) guiding him along a syncretist path. Paul took popular elements of Roman, Egyptian and Persian religions, and expressed the message of his religion in whatever form was most acceptable to the Empire as a whole.
The most popular religion with the Roman military was Mithraism. It was exclusively male, a mystery cult with seven levels of initiation, and a clear-cut view of the world as the battle-ground between good and evil. It promised eternal life to its believers, and its god was Mithras, the Unconquerable Sun.
For an extensive review of the whole issue, I refer you to Ben Best’s enormous review of the roots of Christmas, from which I quote:
“Mithras was a divine being borne of a human virgin on December 25th (the Winter Solstice by the Roman Julian calendar), his birth watched and worshiped by shepherds. As an adult, Mithras healed the sick, made the lame walk, gave sight to the blind and raised the dead. Before returning to heaven at the Spring Equinox Mithras had a last supper with 12 disciples (representing the 12 signs of the Zodiac). Mithraism included Zoroastrian beliefs in the struggle between good & evil, symbolized as light & darkness. This militaristic black-and-white morality (including a final judgment affecting an afterlife of heaven or hell) probably accounted for the popularity of Mithraism among Roman soldiers. Mithraism was like an ancient fraternity: a mystery cult open only to men which had seven degrees of initiation — including the ritual of baptism and a sacred meal of bread & wine representing the body & blood of Mithras.”
The purple-robed priests, candles, incense, circular wafers and Queen of Heaven motifs were ideas that were familiar and attractive to Egyptians. The winter solstice greeting cards and presents, the greenery of trees and branches and garlands, the pantheon of saints to pray to – those customs were comfortable among Greeks and Romans. But the December 25th Virgin Birth (along with much else) was what would make Paul’s Christianity completely familiar and acceptable to the Roman Legions.
In The Gospel According to the Romans, the Roman military are Mithraists while Jesus and his followers are Jews. There weren’t any Christians yet, of course.