What does the Latin word "circa" mean when preceding a date?

Circa (from Latin, meaning 'around, about, roughly, approximately') – frequently abbreviated c., ca. or ca and less frequently circ. or cca. – signifies "approximately" in several European languages and as a loanword in English, usually in reference to a date. "Circa" is widely used in historical writing when the dates of events are not accurately known.

When used in date ranges, "circa" is applied before each approximate date, while dates without "circa" immediately preceding them are generally assumed to be known with certainty.