Quote:December 25th marks the day after the winter solstice and became associated with Deus Sol Invictus (the Sun God) who was introduced as Rome's principle deity by the emperor Elagabulus (Varius Avitus Bassianus--reigned 218-222 CE) and again Aurelian in 247 CE.
Which in turn was merely an adaptation of the Roman Saturnalia festival (which dates back to 217 BC) so, people were well used to partying at this time of year.