Rabb Family in South Carolina: the 1850 Census

My third great grand uncle, J. Glazier Rabb in 1850 Census in Fairfield, South Carolina (15 Aug 1850): He is the head of the household.  At the age of 33, his occupation is "Planter".  (See discussion at THIS LINK).  
See also the wikipedia article.

 The value of his real estate is $5000; I am assuming that he inherited this property, for the moment.  So, if he was 33 in 1850, he was born about 1817.  

Mr. Rabb is married to Nancy; for both her and her husband, they were recorded as having been born in Fairfield County.  Nancy is age 28.  (She was born about 1822).  From various sources, I believe that her maiden name was Watt.  In my database, she is listed as Nancy Ann Kinkaid Watt.

Their oldest child living at home is John W. Rabb (age 9).  Then, there is James K. Rabb, age 6; William C. Rabb, age 5; Virginia C. Rabb, age 2, and a baby (no given name is recorded).  This child is 1/12 years old.  Can we "guestimate" that the child was born in July of 1850?  We will want to follow up our research by checking the 1860 census, etc.

Here is the findagrave link to John Glazier Rabb.