I made Thanksgiving "The Big Game", kicking out the gnomes and adding watching sports. Valentine's Day was trimmed considerably, so now it's just Romantic interactions and...drinking, because single sims have their own activities. As far as new holidays go, in another save I made a "Feast of Caritas" to replace Valentine's and it's basically different types of...love? Activities include telling stories, being romantic, being thankful, and remembering the dead. It's circle-of-life kind of celebration, I guess. One of my Sims also has a holiday named after her, and the day's activities are her favorite things. I think it's "Celebrate Sage" or "Sage is Awesome Day", something flamboyantly unimaginative. I have versions of her in Sims 2, 3, and 4, and she's basically an uber-sim who works constantly to perfect herself while also trying to take over the town and create clones and/or androids.
