The Value of "Circa" in Birth or Death Dates

In attempting to include birth and death dates for as many authors in the bibliography as possible I realized that for most ancient authors the birth or death dates may be uncertain. This was an issue that I had not thought about in detail when planning the programming of the site. However, as I painstakingly reviewed every author of the many thousands in the database during the month of May 2015 I realized that without an indication of uncertainty I could not accurately enter birth or death dates for authors where this information is primarily an educated guess. 

To remedy this situation I asked Jessica Gore to put in switches next to the birth and death dates on my control panel so that I could indicate when one or both of these dates is uncertain. You will see that reflected in the use of the word "circa" for a birth or death date when that is the situation.  It is particularly true for ancient authors when both birth and death dates are estimates. For medieval authors sometimes the death date is known but the birth date is uncertain, and the situation can also apply to sixteenth or seventeenth century authors. For later authors when there is no information available, rather than putting in guesses, I have typically just left out this information.