New Year's Eve is a day that falls on December 31 on the human calendar. At least for present-day humans, it is a time of celebrating the passage of the old year and the arrival of the new year, usually by waiting for the clock to strike midnight before letting loose confetti and a festive cheer while singing the classic song "Auld Lang Syne."
Empath: The Luckiest Smurf stories
In the EMPATH: The Luckiest Smurf story series, the Smurfs celebrate New Year's Eve in the same manner as modern-day humans. During the events of "Days Of Auld Lang Smurf", however, the Smurfs dealt with the mysterious presence of the parent Smurfs (Papa Smurf's generational peers) coming back to life.
As Smurfette, Polaris Psyche, Grouchy, and the Smurflings found out, this "resurrection" turned out to be nothing more than a spell cast upon them by Chlorhydris the witch with the intention that the spell would kill those who are under its influence by midnight on December 31 when the "resurrected" parent Smurfs would instantly vanish. Baby Smurf used a counter-spell on the Smurfs that made them see the truth for themselves long before the original spell would wear off, thus foiling Chlorhydris' plans.
LD Stories/Expanded AU
Within The Light and Dark Series, which crosses over with the Expanded Animated Universe, New Year's Eve is primarily celebrated by humans and Smurfs. In the Season 11 episode, "A Hovel is Not a Hospital," the Smurfs throw a party, partly to celebrate Moxette's first New Year's, while Johan ventures out in desperation to find someone who will cure a deathly ill Scruple before his time has run out.