In my genealogy research, I found no less than 5 documented birth dates for my grandfather that differed from his birth certificate. These dates spanned 12 years and two seasons! I obtained copies of his birth certificate, the passenger manifest on the ship from Ireland to the US, census information in Ireland, multiple census records in the US, his immigration and naturalization papers, and his World War I draft registration card. As the years progressed he failed to age at the proper rate. That leads me to guess as a laborer he wanted to appear younger to keep his employment. There are still two living siblings of my father. However, neither has the slightest idea of their father’s birth date or even the season. Hard to imagine they never celebrated his birthday. Although, as a child I don’t remember a birthday party for him either.
Thank goodness my grandmother told the truth about her birthday. It was a treat to see everything match when I obtained similar records for her.