Even though you are admitted to the U.S. for "duration of status", you must still be attempting to complete your studies by the program end date located under the “program of study” section on your I-20. This date is an expected date of completion for the degree program that you were admitted for. Under certain circumstances you may have to extend this end date. The delay must be caused by compelling academic or medical reasons, such as changes of major or research topics, unexpected research problems, or documented illnesses. Please note that delays caused by academic probation or suspension are not acceptable reasons for a program extension. The application for extension may be made at any time before your I-20 expires, but not after. Failure to apply for a program extension before the expiration date will mean you have violated your F-1 status and you will have to apply for reinstatement.