This is the date when the birth of Christ is celebrated. Although it is generally recognized that His birth was in the springtime, this date has been adopted for the celebration.
This midwinter date was already a celebration in earlier Roman and Egyptian cultures (and many others), and has a sullied reputation as being a “pagan” occasion. It is thought that Christianity appropriated a pre-existing celebration and put a Christian veneer on it. That is true enough, as far as it goes.
If you go back far enough in religious observances, there was a mid-winter celebration that existed from antedeluvian times that marked the return of light and the promised triumph of light over darkness. The “pagans” got it from an original true tradition and then corrupted it into Rome’s Sol Invictus and other festivities.
Although this is not Christ’s birthdate, and although it was acknowledged in false religious traditions at the time they were Christianized, yet this date was always an important yearly milestone. It reflects the intention of God to eventually have this world reclaimed from darkness and brought into peace.
“For thus says the Lord: Behold, I will extend peace to her like a river, and the glory of the gentiles like a flowing stream.” OC Isa. 25:2 It is therefore apt to celebrate the birth of the Lord on a date when nature promises the triumph of light. “For unto us a child is born, unto us a son is given, and the government shall be upon his shoulder. And his name shall be called Wonderful Counselor, the Mighty God, the Everlasting Father, the Prince of Peace. Of the increase of government and peace there is no end, upon the throne of David and upon his kingdom, to order it and to establish it with judgment and with justice from henceforth even for ever. The zeal of the Lord of Hosts will perform this.” OC Isa. 4:1 Our Lord will triumph. He came in meekness and will return in glory.