The reason Christmas is on December 25th is actually a mix of religious tradition, historical calculations, and cultural adaptation. Here’s the full picture:

1. Early Christian history:
   The exact date of Jesus’ birth is not mentioned in the Bible. Early Christians didn’t initially celebrate it, focusing more on Easter (Jesus’ resurrection).

2. Link to the winter solstice:
   December 25th closely follows the winter solstice in the Northern Hemisphere (around December 21–22). Ancient peoples celebrated the solstice as the “rebirth of the sun” because days start getting longer. Some scholars believe early Christians picked this date to align with these existing festivals, making it easier to spread Christianity.

3. Roman festival influence:
   The Roman holiday “Dies Natalis Solis Invicti” (“Birthday of the Unconquered Sun”) was celebrated on December 25th to honor the sun god. Christianity eventually adapted this day to celebrate the “light of the world” — Jesus.

4. Calculation theory:
   Some early Christians calculated Jesus’ birth based on the belief that he was conceived on March 25th (the same day as the spring equinox). Counting nine months forward leads to December 25th.

5. Official recognition:
   By the 4th century, the Church officially celebrated Christmas on December 25th, solidifying it as a Christian holiday.

So, in short, December 25th was chosen as a combination of symbolism (light, new beginnings), practical adaptation of existing festivals, and early Christian calculations—not because there’s a historical record of Jesus being born on that exact day.