Saturnalia is finally here. Today (a.d. XVI Kal. Ian.) is the first day of the very popular Roman's winter solstice celebration. In Cicero's day, the festival lasted 7 days. The author of a work called Saturnalia, Macrobius, says the festival originally began on the 19th, but was pushed back to the 17th with the calendar reform by Julius Caesar. Although it was a festival for Saturn (and Ops), with religious rites and a public banquet, it was also a private festival, with gift giving and role reversal. Slaves were allowed to gamble and didn't have to work.
Read more about Saturnalia
Mary Beard offers some suggestions you might be able to adapt for a modern Saturnalia: Five things the Romans did at Christmas.
"This day in ancient history" caveat: please see Unreliability of Dates.