He was recorded in the 1850 census as age 3 months. If that age was reported as of June 1, as it is supposed to be, then it would mean he was born during Feb 1850 (a child born in March would not turn 3 months until some time in June.) If he was reported as his age on the date of the census visit, though, which was more commonly done than following the rules, then it would mean he was born in April. So I’m putting “about March”.