One thing I love about the holidays in the Sims 4 Seasons expansion is that you can customize them. Not only can you create your holidays, but you can also edit existing ones. To make a holiday longer in Sims 4, navigate to your calendar icon. There, you can click on a holiday to make edits and there’s a plus button to add your holidays and traditions. The calendar is available to everyone with the Sims 4 base game, though it has holidays and advanced features with the Seasons expansion pack.