How can a man be born on marchhave his birthday on may?

A man can be born in March and have his birthday celebrated in May if he was born in a location where the calendar system varies, such as in a region that follows a different calendar (like the lunar calendar). Additionally, he might have been born on a leap year, where his birthday could be officially recognized on a different date. Alternatively, it could simply be a personal or cultural choice to celebrate his birthday in May instead of March.