Why is Christmas, the birth of Jesus the Christ, on the morning of December 25th?

Does this mean December 25 is actually Jesus Birthday? The short answer is No. The medium answer is there is no trustworthy evidence for pointing to the precise date. The longer answer is that it doesn't matter, and you're missing the point if you are focused on the literal and the actual.

Christmas is about the birth of Christ, as an archetypal incarnation of eternity, a motif of the redemption of all life by joining the divine with the temporal. "The Word made Flesh and dwelled among us." as in John’s Gospel. Or T.S Eliot’s lines from the Four Quartet’s

Time past and time future

What might have been and what has been

Point to one end, which is always present

The primary symbol that contains this revelation of redemption is light and darkness. John’s gospel continues, “The light shines in the darkness, and the darkness has not overcome it.”

When Christianity migrated north out of its Mediterranean and Jewish cultural background, it encountered the Celts, primarily in Ireland. The cycles of the moon were dominant in the Jewish calendars. Still, the seasons' processes were prevalent in the northern lands where winter, spring, summer, and fall and the accompanying planting cycles were more dominant. As the two world views interacted, they merged some of their rituals.

If the light coming into the world is the central message of Christmas, then it makes sense that this event would happen when northern European tribes celebrated the birth of light in the winter solstice. Now to the naked eye, it seemed that time stood still in the four days following the winter solstice. Those days of Dec 20-24 had no discernible change in the quality or quantity of light, but on December 25th, ah then one could see the light growing.

While some people view Christianity as a relatively rigid dogmatic religion, its history is much more pliable. Many of our religious and cultural practices are mergers and adaptations to existing cultures.

If you’d like to read more about the evolution of Christmas, I commend you to the work of Alexander John Shaia https://www.quadratos.com.

In the meantime, let the light shine in you and our world.