Correction in dob

Hi, This is a very genuine problem which im facing from many years but couldn't solve it due to lack of knowledge. My query is very basic but it's going to help me n make my future even more better if I could get some good n executable advice from you... My query is how can I change/ correct the DOB ?? I n a graduate and in all my certificate the dob is wrong I.e the birth year is wrong...n because of that...on my other legal documents the same wrong dob has been written...n as time passed I couldn't know how to solve this matter....I have no proof of my original birth certificate ..what I have is my educational documents..where the wrng dob is printed.. I want to do much better things in life...but I am not able to as we know how our is a age limit n qualification criteria to be followed for any exams.... I know it's very late to ask these stuff but as I mentioned lack of knowledge....but it is well said that it's never too late to begin.... So I request you to please help me in the same... Waiting for your response