What is the time limit to join the university in USA after the visa approval

My F1 visa approved on 28th dec 2015 for Jan admission in USA University but due to some reasons admission deferred for Fall semester in August 2016, For that i would like to know do i need to go for visa interview again and get an approval

or can join for Fall semester with the existing visa. Please clarify.

We have been told by one of the readers that, if you are going to the same University, you do not need new visa stamping, the 5 month rule does not apply. They have sent us the confirmation emails from CBP as well. You will need to get a new I20 from the school though. You can write to CBP support desk and check the same, if you need confirmation. You can check with your school DSO and CBP to validate the same.