Um check which day it is? I dont know about in your timezone or where you are - But most of Europe give their employees free or early days on this day..
Not to mention that there is a ton of post to go through for them.
That said, you use mods, have you tried without useing them, alot of times mods will bloat your savefiles to crazy sizes.(in other games, I dont use mods yet in this game, but say in Skyrim or Fallout the vanilla savefile is tiny, vs the modded version to put it mildly)(4k vs 15k in Fallout that I just looked at now quickly(granted I notice it much).
So compare the size of a clean savefile vs your modded version.
In my case my starting save is about 9k and now at about 1000 days in(bit shorter) its 9,6k so marginal difference.
While some may suffer from memoryleaks etc, overall its fairly good and much more likely that your mods is the cause of it in this case.
They have been very good at adressing memoryleaks before, and if you are experienceing it on a clean save I'd be sure to provide them with a savefile so they can examine it.
Um, check the thread list? TW responded to several threads made after mine. I just hope they're at least aware of this problem, I'm not the only person who's experienced this recently, that person on Reddit I mentioned has a very similar issue on the same patch, they claimed they had 0 mods.
What patch is your 1000 day save on?
I disabled all the mods I had and loaded up my game and made a new save, the game still took forever to save. I checked the size of the save files, my save at 600 days in is only about 20.9k KB while my 1000 day save is double that, 41.8k KB. My game at 300 days is even less than that, at 10.4k KB. Where this save bloat is coming from I have no idea, like I said my mods are only cosmetic, fire arrows, torches, banners on some units etc. When I disabled the mods and made a save, that save's size decreased by about 3k KB, but made no difference in the time to save the game.
I suppose it could be because of the mods, but why would they be causing issues now and not before? My issue began right around the time they released their most recent hotfix.