One thing which needs to be looked out for is the date a given US census is linked to.  The earlier censuses which have each individual’s age included, i.e. 1850-1900 are each based on the age of the person on the first of June.  1910 is based on April 15; 1920 is based on January 1, and 1930 is based on April 1.  This means that when an age is expressed in months, you have to work backward or forward to get the correct month of birth.  Even then they can often be off a month either because census taker calculated wrong, or because the exact day of birth isn’t known (this would mostly be the case for the 1910 census.