John James Downes, born in Ireland in 1882 and arriving in the US in 1883, applied for a social security number in 1942 in Lakeland, Florida. He gave the correct date of birth (May 12th) but added 9 years to the date making it 1891 instead of 1882. He also subtracted 10 years from his age saying he was 50 and gave his place of birth as Queens, New York instead of Ireland. All other details are correct; parents' names, place of employment, where he lived, etc.
I'm wondering if you couldn't apply for a social security number if you were 60 or thereabouts. That's the only reason I can come up with for doing this. Unless, of course, he had already lied about his age when he married and he wanted to be consistent.
He knew his correct date of birth when he registered for the WWI draft as a naturalised citizen.