I noticed the past few parties I've had that the timer seems to be broken. I'll start a party and the timer might be red and show a short time left. Then, once that time counts down, it might show an hour left, and so on. Basically, it's all over the place. The parties seem to last the right amount of time, but sometimes I like to know how much time I have for completing goals and that's pretty much impossible.
I've also noticed an increase in "musical chairs," especially at dinner parties.
EDIT: There's a bug thread for it here:
http://answers.ea.com/t5/The-Sims-4-Bug-Reports/OPEN-Party-timer-not-displaying-time-remaining-properly/m-p/5144678#M21810
