The winter solstice was celebrated in countless places, including China and Persia, the latter regarding the solar Lord and Savior Mithra's birth.
In Rome, a great festival called "Saturnalia" was celebrated from December 1st to the 23rd.
The winter solstice festival in Egypt included the babe in a manger brought out of the sanctuary.
The well-known solar feast...of Natalis Invicti, celebrated on 25 December, has a strong claim on the responsibility for our December date....The earliest rapprochement of the births of Christ and the sun is in Cypr., "De pasch. Comp.", xix,
"...O, how wonderfully acted Providence that on that day on which that Sun was born...Christ should be born."
"...But Our Lord, too, is born in the month of December...the eight before the calends of January [25 December]... But they call it the 'Birthday of the Unconquered'. Who indeed is so unconquered as Our Lord...? Or, if they say that it is the birthday of the Sun, He is the Sun of Justice."
"spoken of by Tertullian, Jerome, and other Fathers of the Church, who inform us that the ceremonies took place in a cave, and that the cave in which they celebrated his mysteries in Bethlehem, was that in which Christ Jesus was born."
"It was the feast of the Dedication at Jerusalem; it was winter..." (RSV)
"For let it be borne in mind that it was precisely at the season of this sacrifice, near the beginning of the new year, that the birth of Mithra was celebrated over all Persia and the world, in temple-caves, on the night of the 24th of December, the night of light. Even the British Druids celebrated it, and called the next day, the 25th of December, Nollagh or Noel, the day of regeneration, celebrating it with great fires on tops of their mountains. In fact, all nations, as if by common consent, at the first moment after midnight of the 24th of December, celebrated the birth of the sun-god, type among the Gentiles of Christ, the Incarnate Son of God, as the Desire of all nations and the Saviour of the world."
"The Baal-fire feast, or meeting, was a great festival in Ireland, on the 25th of December, and midsummer eve. Baal, or Bel, was a name of the sun all over the east."
"Jesus is the reason for the season."
When Was The First Christmas?
Excerpted from "Suns of God: Krishna, Buddha and Christ Unveiled" by Acharya S
¹ This citation contained a typo that unfortunately ended up in the "Reason for the Season" video. As here, it should be Josephus's Antiquities, XII, 7.7, rather than book XIII.