I post this every year for the edification of the unknowing:

THE ORIGINS OF CHRISTMAS

Due to the origin of Christianity in Judaism, the early Christians celebrated their Sabbath on Saturday, like the Jewish Sabbath, not Sunday! And in the early years of Christianity, Easter was the main holiday; the birth of Jesus was not celebrated. Indeed, there was still controversy on whether Jesus had been divine since birth, or if he received divinity when he was baptized by John. Finally, in the 4th century (336 AD) Christian Church officials along with the Roman Emperor Constantine decided to institute the birth of Jesus as a holiday. By 354, the Roman Bishop Liberius had associated the Jesus' birth with Saturnalia. 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 pre-existing and immensely popular Roman Saturnalia festival. First called the Feast of the Nativity, it spread to Egypt by 432 and to England by the end of the 6th century. By the end of the 8th century, the celebration of Christmas had spread all the way to Scandinavia. But, even as late as 742, some Christian leaders were still warning newly-converted Christians against Pagan celebrations: Bishop Martin of Braga, in 575, warned:
“You shall not perform the wicked celebration...and observe the holiday of the Pagans, nor shall you decorate your houses with laurel and green branches. This whole celebration is Pagan”.

And in 742, the Northumbrian missionary Bishop Boniface warned his German (“barbarian“) converts against celebrating the solstice.

The book "Holy Blood, Holy Grail" discusses the pragmatic political motives of the 4th century Roman Emperor Constantine, who along with Pope Julius I, first moved the celebration of Christmas to December 25. The authors claim that Emperor Constantine actually followed the cult of Sol Invictus, a form of sun worship that was imposed by Roman emperors on their subjects a century earlier. But:

"His primary, indeed obsessive, objective was unity -- unity in politics, in religion, and in territory. A cult or state religion that included all other cults within it obviously helped to achieve this objective...In the interests of unity, Constantine deliberately chose to blur the distinctions among Christianity, Mithraism [another Sun cult of the time] and Sol Invictus..."

Roman Emperor Constantine also decreed that Sunday -- "the venerable day of the sun" would be the official day of rest, not Saturday!

So, what is Saturnalia? Saturnalia was the Roman midwinter celebration of the Winter Solstice and named for Saturn, God of Agriculture. Saturnalia was the greatest of all the Roman annual holidays! The Winter Solstice is around December 21 and marks the shortest day (daylight hours) of the year, meaning the Sun has reached its lowest point (nadir) from the horizon for that year. ("Solstice" is a Latin word originally derived from sol sun + status, the past participle of the Latin sistere to come to a stop, cause to stand.)

Originally, the Romans only celebrated one day as Saturnalia, but later, during the days of Empire, the celebration was officially extended to a week, December 17 - 23. This was the most popular holiday of the Roman year. Catullus describes it as "the best of days," and Seneca complains that the "whole mob has let itself go in pleasures." Pliny the Younger writes that he retired to his room while the rest of the household celebrated. Cicero fled to the countryside. It was an occasion for celebration, visits to friends, and the presentation of gifts, particularly wax candles, perhaps to signify the returning light and the longer days after the low-point of the solstice.

Saturnalia began with the sacrifice of several young pigs at the Temple of Saturn, where free meals were provided to any members of the public who wished to feast and celebrate. After the feast, the celebrants shouted “Oy, Saturnalia”! This also became a standard greeting among the populace during the holiday season.

During the holiday, restrictions were relaxed and the social order reversed. Gambling was allowed in public. Slaves were permitted to use dice and did not have to work. Even children were known to gamble, using nuts as wagers. Instead of the toga, less formal dinner clothes (synthesis) were permitted, as was the pilleus, a felt cap normally worn by slaves. Slaves were treated as equals, allowed to wear their masters' clothing, and be waited on at meal time. Punishing criminals and starting wars were also not permitted during Saturnalia.

The biggest part of Saturnalia was attitude more than decoration. Feasting, drunkenness, merrymaking, hopefully the conception of more children (or at least enjoying those activities which led to conception!), pranks, gift giving, role reversals (not true ones, only symbolic ones - slaves weren't really free to make a freedman's decisions and anything they did or decreed would reverse at the end of Saturnalia.)

It was traditional to deck the halls with boughs of laurel and green trees as well as a number of candles and lamps. These symbols of life and light were probably meant to dispel the darkness. Also, in later times, a Roman tribune made a law that only a candle could be given to a richer person by a poorer person, because the habit of giving lavish Saturnalia gifts was impoverishing the poor (and enriching the rich).

List of Saturnalia traditions which continue to this day:

Sacred Flames -- candles lit and new fires kindled to represent new Solar year.
Greens -- Holly given with gifts, homes decorated with wreaths and garlands.
Time Off from Work -- government, schools, businesses closed; multiple days off.
Peace -- dispensing of punishments suspended and courts closed; wars ceased.
Relaxing with Family and Friends -- renewing bonds, sharing celebration.
Gift Giving -- dolls to children, candles to friends; fruit symbols representing increase.
Feasting -- sharing food with family and friends; on-going eating and drinking.
Helping Less Fortunate -- class distinctions suspended; food for all; masters waiting on servants.

Among the “Northern Barbarians“ (Germanic Tribes) and the Gauls (Celts) of France and England's Celts, the Mid-Winter Festival of Saturnalia existed as “Yule“, with similar traditions. Yule logs were burned during this time and wooden wheels symbolizing the Sun were set on fire and rolled down hills. This symbolized the “return of the Sun” as the days began to get longer after the Winter Solstice.

The name Saturnalia eventually died out, but its celebrations, such as decking houses with evergreens, giving presents and feasting, were attached to Christmas. But the Pagan celebration of the Calends of January (New Years) remained a “heresy” and was never officially assimilated by the Christian Church.

MISTLETOE:
The Christmas tradition of “kissing under the mistletoe” also has strong historical roots. Long ago, mistletoe was used as medicine by the womenfolk in the same way that “morning after” birth control pills are used today! This practice survives today as the comparatively innocent “kissing under the mistletoe”.