Similar confusion might have occured in case of birthday of Raja Shivaj.

The calendar followed in India at that time was Shaliwahan shak,birtdate recorded accordng to that date was falgun vadya trutiya, i.e.18th day of the last month  in that Calendar,which generally falls at the end of March or around that date, But according to British historians the birthdate was noted as19th February as per Gregarian Calendar It is now accepted as the official birthdate in Maharshtra