Circa (from Latin, meaning 'around, about'), usually abbreviated c., ca. or ca (also circ. or cca.), means "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. For example:
1732–1799 or 1732–99: both years are known precisely.
c. 1732 – 1799: only the end year is known accurately; the start year is approximate.
1732 – c. 1799: only the start year is known accurately; the end year is approximate.
c. 1732 – c. 1799: both years are approximate. Wikipedia