Saturnalia begins
Rome's festival of Saturn began with a public banquet and the cry 'io Saturnalia'. It later stretched to 23 December.
Background
The Saturnalia, honouring the old god Saturn, was Rome's most loved festival. It began on 17 December with a sacrifice at the temple of Saturn in the Forum, followed by a public banquet; the woollen bonds on the feet of Saturn's statue were loosened for the festival per Macrobius and Statius. Originally one day, it later stretched to several; Augustus set three days and Caligula added a fifth, and by the late empire it ran to 23 December per Macrobius 1.10.
During the festival, business and courts stopped, people swapped the toga for casual dress and the felt cap of freedmen (pilleus), gambled openly, and gave gifts: wax candles (cerei) and small pottery figurines (sigillaria). Catullus called it "the best of days" (14.15). Households let enslaved people eat with, or be served by, their owners, and speak freely per Macrobius, Accius quoted by him, and Seneca.
These reversals were real but temporary; the enslaved returned to their condition when the holiday ended. Seneca, writing in December, notes that the whole city seemed to go wild while he debated whether a wise man should join in per Seneca, Ep. 18. Many Saturnalia customs—feasting, gifts and candles—later fed into Christmas and New Year traditions modern view; the exact links are debated.