U.S. enumerators were suppose to record the household's information as of the official census day -- not the actual date of the enumeration. Of course, we have no way of knowing who followed these instructions and who did not. However, the official census days were: First Monday in August for 1790-1820 schedules June 1 for 1830-1880 First Monday in June for 1890 (most of this schedule was destroyed or badly damaged by a fire in 1921) June 1 for 1900 April 15 for 1910 January 1 for 1920 April 1, for 1930 For more about census records see RootsWeb's Guide to Tracing Family Trees on the subject: http://rwguide.rootsweb.com/lesson9.htm