New Year’s Eve celebrations will start at 6am throughout the major cities of Azeroth. Every hour there’ll be fireworks and drinking and dancing of course. Apart from the fun, the celebrating offers some practical perks. Dancing will give you the “Celebrate Good Times” buff that adds 10% to all your stats for 30 minutes. Drinking a Filled Festive Mug will give you the “Lightheaded” buff with a slowfall effect for 1 day. So, drink all you want and if you fall off your flying mount you won’t get hurt, provided you don’t land in lava or a pack of hell boars. Mobs don’t like to get hit by flying drunkards.
Here’s a video of some of the fireworks. It’s over 12 minutes long but you’ll get the gist of it after about 1 minute: