Some Important Considerations
First: England did not adopt the Gregorian calendar until 1752, so the dates for Christmas in the Middle Ages are off approximately 12 days from modern dates. When England officially changed to the Gregorian calendar, they made September 1 September 14 to account for discrepancies.
Second: Christmas was not a time when differences were forgotten. There were no times in the Middle Ages when classes could be forgotten; although the lord of a manor might have provided extra food for his serfs, and allowed them to even sleep in the great hall of the manor, or even allowed the practice of mumming, he and his family were still completely separate from their social inferiors. Even in church, there was no equality. The more social status one had, the closer he/she got to stand and kneel to the altar. Men and women were separated, and men celebrated the Eucharist first.
Third: the literacy levels in the Middle Ages in England were somewhere between 5- and 10% of the population. As a result, few people knew exact dates or kept track of years. Instead, they used holy days, especially the group of days in December and January (Feast of the Immaculate Conception, Christmas, Slaughter of the Innocents, Epiphany), to keep track of time. (Years were measured in terms of a king's reign; i.e. "the fourth year of Edward II's reign.")
Fourth: the origin of the English word "Christmas" is found in the Old English Cristes Maesse (Mass of Christ).
Evergreens, Mistletoe, and Yule Logs
Houses were decorated with evergreens. Since pagan times evergreens were revered for their ability to remain green, and in some instances produce berries and flowers, through the winter. They were used to symbolize everlasting life. Holly, ivy, and evergreen herbs such as bay and rosemary were the most common, and their meanings were also linked to pagan beliefs. Rosemary was for remembrance; bay for valor; holly and ivy were a particularly popular combination, because the holly was traditionally thought to be masculine and the ivy feminine. Therefore a sprig of mistletoe made a balanced pair which gave stability to the home. Hanging mistletoe above doorways was related to the Norse worship of the goddess Freya; because England had many people of Norse and Viking descent, it had many influences from those religions. Mistletoe was not yet the kissing ploy that it is today; however, there were sprigs of holly and berries under which no lady could refuse a kiss.
The Yule log is another throw-back to England's Nordic roots; in Scandinavia, where it is dark and cold during the winter months, fire is exceptionally important. In the medieval period, the Yule log was ceremoniously carried into the house on Christmas Eve and put in the fireplace of the great hall of a manor (nearly every village and town had a manor of some sort; if the lord or lady of the manor was not present, the caretakers would perform these duties). Often decorated with greenery and ribbon, it was lit with the saved end of the previous year's log and then burnt continuously for the Twelve Days of Christmas, providing much needed light and warmth.
And at Midnight...
After fasting for at least twelve hours, the people would go to Mass. Before they went, they would feed the animals, to celebrate that Jesus had been born in a stable surrounded by donkeys, cows, chickens, and other animals. At midnight, Jesus gave animals the power to speak, and they would talk freely, or so the story went. This was convenient, because everyone was inside the church and could not hear the animals speaking.
In Medieval England there were, in fact, three Masses celebrated on Christmas Day. The first and most characteristic was at midnight (the Angel's Mass), catching up the notion that the light of salvation appeared at the darkest moment of the darkest date in the very depth of winter. The second Christmas Mass came at dawn (the Shepherd's Mass), and the third during the day (the Mass of the Divine Word). Spoken entirely in Latin (except for the homily), the Mass was often over two hours long. It contained all of the elements of a Mass as we see it today-- Church tradition evolves slowly-- such as the readings from the gospel, the homily, the Eucharist. It involved the first singing of hymns that would later become Christmas carols (becase the Mass was so long, priests invented interactive songs to make it more interesting). Another interesting addition to make a long Mass more interesting was the tropes, which would evolve into the liturgical mystery plays. These were enactments of Biblical stories that were so outrageous that the Church ruled them blasphemous and demanded that they be phased out. By the time of the Reformation, they were completely gone.
Also important in the celebration of Christmas was the banquet, which necessarily varied in sumptuosness with the resources of the celebrants. The menu varied with soups and stews, birds and fish, breads and puddings, but a common element was the Yule boar, an animal for those who could afford it or a pie shaped like a boar for more humble tables. Often the lord of the manor would host all of the people in the village in the great hall for a feast.
Mummers and Lords of Misrule
A popular custom was mumming, in which revelers put on masks or the clothes of the opposite sex and, accompanied by minstrels and musicians, traveled from house to house. This stems from the ancient Greek and Roman rites of Saturnalia, in which slaves were freed for a day. Another custom (practiced particularly in the universities) was the appointment of a Lord of Misrule, who, dressed in gaudy or outrageous clothing, presided over the holiday merriment with the pomp and circumstance of an actual monarch. The Lord of Misrule sometimes led revelers on wild nighttime processions through town, which of course angered the resident church leaders. However, churchmen had their own form of this custom--the appointment as a young boy as bishop for the holiday season. Lords usually chose this time to bestow gifts upon their servants; a common present was a new suit of clothes.
And the party continues...
A Medieval Christmas celebration was not over in a day, but continued until January 6th (the Egyptian winter solstice), and also the Feast of the Epiphany on the 12th day after Christmas Day. Epiphany celebrated the visit of the wise men, the Magi, around whom many layers of legend accumulated as they came to be conceptualized as three oriental kings who visited the infant Christ at Bethlehem in Judea. Epiphany also symbolized the manifestation of Christ to the Gentiles. The Monday after Epiphany was called Plough Monday, and it was then that ploughing began.
The day after Christmas recalled St. Stephen, the martyr mentioned in the New Testament book of Acts. The following day was that of John the Apostle and Evangelist (not to be confused with John the Baptist), and 28 December was Holy Innocents' Day or Childermas Day, commemorating the male children killed by Herod. It was superstition that the day of the week upon which Holy Innocents' Day fell would be unlucky for the coming year.
There was no absolute standard about ending the Christmas season with Epiphany, and many carried it through to forty days after Christmas, the date of an ancient pagan festival on 2 February. This is now celebrated as Candlemas, or the Feast of the Purification of the Virgin, or alternatively as the Presentation of the Infant Jesus in the Temple. In one of the most elaborate processions of the year, all parishioners came to Mass with a penny and a candle blessed before the procession, both of which were offered to the priest as part of the parochial duties of the faithful. Other candles were blessed and taken away by the faithful to be used for such things as giving comfort during thunder storms or while sick or even dying. Such candles were thus important for giving people a light of solace in the face of hostile forces and stressful events. Candlemas was a closure for the long season commencing with Advent.