Prepared by Elisabeth Lindsay.
An enumeration date commonly refers to the "official" or control date set for a particular enumeration event such as a census. The official enumeration date may vary from one enumeration to the next. The enumeration date is a control function for collecting data over a broad space of time. All data collected is based on its validity "as of" a single date, no matter what date the information is taken within the enumeration period.
Most relevant to genealogy, perhaps, are enumeration dates as applied to the census. Because the actual enumeration may have taken weeks or months to complete, enumerators were instructed to record information for all persons as it existed on a particular date, regardless of when the information was gathered. Therefore, the official enumeration date (also known as the census date) may be different than the date on which the census taker visited the household and the actual information was taken. For example, in the U. S. between 1830 to 1900, June 1 was designated as the enumeration date, so persons questioned in mid-August would be asked their age "as of June 1" that year. Although the practice was not strictly adhered to by individual census takers, knowing the enumeration date for a particular census year may shed light on dates and events as they appear in the census record.