A new year's bash is a type of party which can be thrown with The Sims 2: Happy Holiday Stuff. A new year's bash can be thrown by clicking the phone and choosing "Throw Party... New Year's Bash". This party is somewhat different from a normal house party, because it will always start at 8 PM.
In a new year's bash, Sims will autonomously make ruckus and noise. Sometimes, other Sims may react to this. At 11 PM, the police may come and break it up, as with any other party, but if not, Father Time will arrive. He will be standing on the sidewalk, so a selectable Sim will need to call him over. The only interactions available for Father Time are talk and call over, which will be available no matter how close a Sim is to him. Around midnight (12 AM), he will start making a ruckus, which all the Sims at the party will join. After a while, he will turn into Toddler New Year. As soon as he turns into Toddler New Year, he will dance smustle. He will fade away and disappear just before the party ends.