Nina would probably be celebrating with her family, doing some traditional Czech celebrations. She's spend most of the day cooking, and would make sure that dinner did not start till the first star was spotted.

However, she would also make sure that her friends/ so's/ anyone else that would celebrate alone would be invited.

Kata, would celebrate with her family or Ali. Or invite Ali over, plus guests. The Hargraves would also host a 'small' party around New Years for their loyal customers. However, most of the town is invited, so they rent out the civic center for the party.