My maternal grandfather was born in what is now Belarus and did not know his birth date, just that it was during Passover, so his children "gave" him a birthday, April 15.  

My father's birth certificate says he was born in NYC on March 30, 1917, but we always celebrated his birthday on March 29, because "my mother said that's the day I was born."

While the notion that that October 22 was the date of the bris and well might be the correct answer in this case, as my family history shows, there are many reasons that exact birth dates are not known.
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Barbara Sloan
Conway, SC