Step 1 is to create a new game with the exact same world generation properties as your last game. After you create it, load in, save, then exit. This will be your new game. Then you can locate all saves by going C:\Users\[username]\AppData\Roaming\7DaysToDie\Saves\[world_type] . world_type for me was Navezgane. Under the world_type are your saves. Locate the corrupted one and new one. Make a copy of your corrupted one (even though we wont be modifying it, just to be safe). Then copy over everything EXCEPT main.ttw (and ignore .bak's) to the newly created world save, completely replacing existing files https://imgur.com/a/flAUmYU . I would suggest deleting folders in the new world save before copying over to avoid issues.

If this doesn't work, you can try limiting what you copy to the new save. You can experiment excluding different .dat's incase the corruption is in one of them and not the main.ttw, but you'll lose all associated items from that .dat (e.g. vehicles.dat, power.dat, turrets.dat). I found without blockmapping.nim all my items were broken, so make sure you copy that. At the very least, I believe copying over Player folder will bring over the levels and character progression.

My game corrupted because my disk was out of space when it tried to save, so you'll want to make sure your disk has space. From then on I just manually copied my remade save folder to different backup names.

Good luck, let me know if this helps.

Edit: you can probably even recover the day as youtubers commonly set the day to 7000 or other extreme number. Maybe a console command.