回複：學校裏把我I20表上的畢業日期寫成5月31日,可是我還沒有

The expiration date of form I20 has to be the graduation date of your institution. It is your responsibility to keep your status legal and current. You should have contact them to extend your I20 to your desired graduation date. Failure to do so means your I20 is canceled and you are out of status. The school can try REINSTATEMENT, but chances are the REINSTATEMENT will be denied. My guess is when they admitted you, your school gives the same graduation date to everyone, for example, all Masters student will get 2 years, all PhDs will get 4 or 5 years. For some reason, you cannot graduate within the specified time limit, but you failed to ask them to extend the I20 so you fell out of status.