How to get Birth Certificate issued for person born before 1968 who has a wrong birth date

Date of Birth issue: Actually, Born on: 02.01.1968. but current DOB as per Passport /Aadhaar/PAN: 27.05.1965, Place of birth is Dokmoka, Karbi Anglong, Assam. HOW TO CORRECT THIS? ------------------------------------------------------------------------------------------------------------------------ •My elder sister and myself were studying in the same class in the same school. While giving transfer certificate, the school teacher thought us of same age and thus recorded our age in the school records. Incidentally, she recorded mine as elder than my sister. •Whereas I am 4 years younger than my elder sister, her DOB is 17.12.1965 as per her HSLC Admit Card and my DOB is 27.05.1965 and as per her DOB I am around 6 months elder than her - which is incorrect. •Parents have little knowledge about the impact of the DOB written by School Teacher and thus did nothing for correction before 10th Board exam. Admit card showed age as 17 years 9 months and 8 days as on 01.03.1983 and this DOB continued in all documents like passport, Aadhar & PAN , and in employment records. I am also equally responsible for not correcting the same in due time. Current document used for DOB: Passport/Aadhar/PAN. No birth certificate available