Re: Sims 4: Seasons Holiday Glitch - HELP!

I would suggest that firstly you try removing all mods & CC to see if this fixes the issue.

• If It fixes the situation you can re-add one at a time to see which one was conflicting with the function/causing the glitch.
  Go to Documents > Electronic Arts > The Sims 4 > Mods
• Delete cache: 
  https://sims4.crinrict.com/en/2014/09/delete-cache-files/
• Repair the game: Open Origin, click 'Game Library' then right-click Sims 4 > Repair Game.

There was a thread last week there we discussed the holiday schedule, but that was a messed up holiday schedule from changing the season length. I added a couple of links that you may help find info about re-setting up the holidays. Please see below for the links and the link to that post last week.
https://answers.ea.com/t5/Game-Information/Seasons-callendar-whoopsie/m-p/7491628#M10842
https://sims.fandom.com/wiki/Holiday
https://simsvip.com/2018/06/16/the-sims-4-seasons-list-of-holiday-traditions-base-game-seasons/

Please let us know how it goes.