I think the Bible indicates that Jesus was born in the fall, just in time for the feast of Tabernacles. We find that the observance of Christ’s birth as a Christian feast day was invented by the Roman Catholic church in the early Middle Ages, to compete with the pagan winter solstice observance of Satunalia. We have a record of the birth of Christ in the scriptures, but no where does the Lord tell us to celebrate the birth of Christ. Rather we observe the Lord’s supper and baptism, in which we remember His death, and identify with His death and resurrection, respectively.
So if Jesus was born in September (let’s say), then He was conceived by the Holy Spirit inside the virgin Mary, in December. The Light came into the world in the darkest part of the year. The incarnation did not happen at the birth anyway, it happened when God sent His Son into Mary’s womb(Gal.4:4) to become human, and dwell among us. Thus His “Tabernacling” among us began nine months before He was born, probably around this time of the year. To us believers, it is joyful to take every and any opportunity to worship Christ and thank the Father for sending His Son to dwell among us, so He could die for our sins as our Savior, and be resurrected in victory over sin, condemnation and death, for all who believe. How grateful and thankful we are! How good and great is our God, in His sacrificial redemption of us, the sinful, lowly “sons of men”.
In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. All things were made through Him, and without Him was not any thing made that was made…And the Word became flesh, and dwelt among us…John1:1-3,14.
But when the fullness of time had come, God sent forth His Son, born of a woman, born under the Law, in order that He might redeem those who were under the Law, that we might receive the adoption as sons (into God’s family) …Gal.4:4-5.