I've changed Winterfest to Christmas Day in my current save, and I also added in Christmas Eve and Boxing Day, both of which are days off work too. Most people have to work on Christmas Eve here in the UK (as far as I know) so I let my sims have the day off off as a treat whenever I add that particular event to a game. I also have New Year's Day as well as New Year's Eve. As I rotate a lot, and almost always on a Sunday morning, I tend to remove the Resolution activity from New Year's Eve and put it in New Year's Day so it's relevant for the family I'm switching to.
I usually delete Brawl Day and sometimes Prank Day, and remove the gnomes from Harvest Fest, and often add a day off of work in the summer but unless I'm playing a themed game, that's about it really.
