With in how many years of completing graduation can one apply for convocation?

There's no universal answer to how many years after graduation one can apply for convocation. The timeframe varies significantly depending on the university or institution. Some universities have a relatively short window (e.g., within a year or two), while others allow applications much later, sometimes with no specific deadline. You must check with your specific university's registrar's office or graduation services department for their policies on convocation eligibility.