Saturnalia

In Rome, where winters were not as harsh as those in the far north, Saturnalia—a holiday in honor of Saturn, the god of agriculture—was celebrated. Beginning in the week leading up to the winter solstice and continuing for a full month, Saturnalia was a hedonistic time, when food and drink were plentiful and the normal Roman social order was turned upside down. For a month, slaves would become masters. Peasants were in command of the city. Business and schools were closed so that everyone could join in the fun. 

Also around the time of the winter solstice, Romans observed Juvenalia, a feast honoring the children of Rome. In addition, members of the upper classes often celebrated the birthday of Mithra, the god of the unconquerable sun, on December 25. It was believed that Mithra, an infant god, was born of a rock. For some Romans, Mithra's birthday was the most sacred day of the year.

In the early years of Christianity, Easter was the main holiday; the birth of Jesus was not celebrated. In the fourth century, church officials decided to institute the birth of Jesus as a holiday.Unfortunately, the Bible does not mention date for his birth (a fact Puritans later pointed out in order to deny the legitimacy of the celebration). Although some evidence suggests that his birth may have occurred in the spring (why would shepherds be herding in the middle of winter?), Pope Julius I chose December 25. It is commonly believed that the church chose this date in an effort to adopt and absorb the traditions of the pagan Saturnalia festival. First called the Feast of the Nativity, the custom spread to Egypt by 432 and to England by the end of the sixth century. By the end of the eighth century, the celebration of Christmas had spread all the way to Scandinavia. Today, in the Greek and Russian orthodox churches, Christmas is celebrated 13 days after the 25th, which is also referred to as the Epiphany or Three Kings Day. This is the day it is believed that the three wise men finally found Jesus in the manger.

By holding Christmas at the same time as traditional winter solstice festivals, church leaders increased the chances that Christmas would be popularly embraced, but gave up the ability to dictate how it was celebrated. By the Middle Ages, Christianity had, for the most part, replaced pagan religion. On Christmas, believers attended church, then celebrated raucously in a drunken, carnival-like atmosphere similar to today's Mardi Gras. Each year, a beggar or student would be crowned the "lord of misrule" and eager celebrants played the part of his subjects. The poor would go to the houses of the rich and demand their best food and drink. If owners failed to comply, their visitors would most likely terrorize them with mischief. Christmas became the time of year when the upper classes could repay their real or imagined "debt" to society by entertaining less fortunate citizens.