What are the chances that my husband has been wrong, all his life, about the year he was born?

He says he was born in 1951. It shows 1951 on his driver’s license. However, the SSA has him listed as born in 1952. We’re going to request a copy of his birth certificate to get this cleared up. But what if his birth certificate even shows 1952?! :O
This is just a kind of fun question, but boy, is the situation a freaking head ache to deal with.

One small bit of background. He said that when he was 16 he lost his driver’s license. His dad went in and got a replacement for him. This was in the 60’s and you could just do stuff like that, without a whole lot of checking and documentation. He said his dad told them the wrong year he was born, which kind of bugs him. It would bug me too if my parents didn’t remember the year I was born.
I don’t know if they put the incorrect information on his replacement DL or if that’s how all this started or what.