go to your game's folder and look into Game, then there will be a Saves folder. copy that to a different spot (entire folder) and replace/delete the old game entirely, and put the save folder back into the game folder, and play again. Should work fine
I think that was intentional, due to some branching choices down the line and certain "forced" scenes, so it won't bug your game if you try to revert the chat. I'd say be glad there isn't a time limit on the number of days progressed. I'm currently 160 days in and only on part 2 of the main story.
