December 17 - The Roman festival of the Saturnalia took placeon this date. The festival celebrated the dedication of the temple of Saturn, the father of all the Roman Gods (equivalent to the Greek Cronus). The festival was very large and on of the most prominent that was celebrated in Roman culture. During the Saturnalia, there were sacrifices and other public rituals, inlcuding untying the ropes that bound the cult statue of Saturn during the other times of the year. In addition, slaves were able to celebrate with a banquet, being served by their masters. Slaves were also free from punsihment, and could even embarrass or disrespect their own maters.
December 18, 218 B.C. - The Battle of the Trebia, the first major conflict of the Second Punic War, occurred on this date. In this battle, General Hannibal of Carthage was able to stun and soundly defeat the army of the Roman Republic, prompting an upheaval of Roman leadership.
December 21, A.D. 69 - On this date, Galba, the first of four emperors in one year takes over rule of Rome. Galba, Otho, Vitellius, and Vespasian all were Roman Emperors in this, the "Year of the Four Emperors".