Turn off autosave, and shut down the game
Ignore save warnings when closing game and restarting. This should work.
Later you can turn autosave back on, or if you want to leave it off, you must save manually before closing game, otherwise you will lose the progress in your career.
Do this before starting a weekend, because if autosave is on when you start the weekend, you will be stuck at the last save it created during that session and you will have to continue.