It's May 31 today, but it shows June 7 in todoist, and every task appear to be undo by today, what happened?
How are you accessing Todoist, through the web version, do you have any plugins/apps as well? Devices?
Have you tried to log out and back in again of those? This could be fixed by doing so.
Are all your tasks dates off by the same amount, are all of them the wrong dates? Have you changed timezones recently?