For centuries, Christians have celebrated the birth of Jesus on Dec. 25. But if you ask historians, they're uncertain what day Christ was actually born.
"There's no way we can know," said religious studies Professor Lynn Ross-Bryant of the University of Colorado at Boulder. "There is simply no historical record."
What historians do know is that the Roman emperor Constantine converted to Christianity early in the fourth century and in an effort to encourage Christianity among his people, designated Dec. 25 in A.D. 336 as the day to celebrate Christ's birth. Constantine chose that day because it best fit with traditions of the time, said Ross-Bryant.
"Dec. 25th was the time for the Roman celebration of the unconquered sun god, Apollo, and this was also the time of the winter solstice," explained Ross-Bryant. "Many religious traditions have a winter solstice holiday which is celebrating the belief or hope that even in this darkest time of the year the light will come back."
According to Ross-Bryant, numerous Christmas traditions also were adapted from previous Greek and Roman religious and cultural traditions.
"It's common in many religious traditions that when a new religious tradition comes into a culture it takes on some of the customs that are already there," she said. "It's a way of making sense to the people -- they know that this is a time to celebrate, and gradually what is celebrated becomes Christianized."
Adaptation of Christmas traditions occurred in many different time periods and parts of the world. In 1225, St. Frances popularized the nativity scene in Italy because the humility of Christ's beginnings fit with his own religious beliefs, she said.
According to Ross-Bryant, other Christmas traditions that are practiced today derived from previous traditions. For example:
* Traditions connected with greenery, such as wreaths and trees, come from Germanic countries and spread to England in the 19th century through Queen Victoria whose husband was German.
* Gift giving probably derived from a combination of the wise men who brought gifts to the Christ child and Santa Claus, or Saint Nicholas, who is an adaptation of European folk customs that had been celebrated in the winter season.
* Christmas carols developed from a custom in which people would sing popular religious songs during feast days, including Christmas. While most other feast days and their songs did not survive the times, Christmas carols are still sung today.