Holiday Issue
@AncientHylian When you say you've changed the season length, did you save it that way and then quit? Be sure to delete the five cache files in your Sims 3 game both initially and after each change. You can experiment on a copy of your save if you want: use "save as" to rename the save, and the original will remain unchanged and listed under the old save name.
These are the five cache files you should delete, all located in Documents\Electronic Arts\The Sims 3:
- CASPartCache.package
- compositorCache.package
- scriptCache.package
- simCompositorCache.package
- socialCache.package
Another thing you could do is delete the file called options.ini, in the same Sims 3 folder as the cache files. You'd need to manually redo all your game settings, which you could do in a temporary new save so as not to even momentarily affect your ongoing saves.
I've also heard of holidays not falling on the assigned day when a season is very short, like maybe fewer than seven days. The game seems not to calculate the correct day, at least some of the time. I'm not sure how long your seasons are, but it might help to permanently lengthen them. If you're open to mods, there are a couple that might help, but I'm not sure whether you want to go in that direction.
