Saturnalia in Rome was a week-long winter celebration, during which the Winter Solstice occurred. It was celebrated for over 500 years.
It was a time of fun and gift giving. People would give each other candles as gifts, as well as sprigs of holly. Small dolls made of porcelain or clay were given to children.
People donned red, soft woolen caps (which remind one of the hats we now pull out of Christmas crackers, or of Santa Hats), and decorated their houses with boughs of greenery. Courts, schools and many businesses closed for the holidays.
People spent their time gambling and feasting. Public banquets seem to have started by 217 BC. Lords of Misrule (Saturnalicius princeps) were appointed for the festivities and feasts. In wealthy houses, it was a time of role reversal, when masters would wait on their slaves.
By tradition, it became as well a period during which you could say what you wanted without fear of punishment, so it was a time for expressing political satire at plays.
In our modern Gregorian calendar, the start of the Roman holiday of Saturnalia now falls on 17 December.
It was originally celebrated just one day, to honour Saturn. With the feast for his wife Ops, though, falling two days later on 19 December, the two soon blended to become three days, and before you knew it, it was a whole week. (the exact dates shifted about a bit until Julius Caesar fixed the calendar, creating the “Julian” calendar.)
Augustus made attempts to reduce the holiday period back to three days; Caligula tried to reduce it back to five days, but even that didn’t really work.
By the middle of the 300s, the Christians appropriated many of the customs. The traditions first became part of Twelfth Night, and later, Christmas.
Saturn was not only the god of sowing fields, he was also the Lord of Mirth and Joviality. The foundations of Saturn’s temple are still in Rome, in the forum.