Astronomical year numbering refers to an alternative method of numbering years in relation to the
Common Era. In astronomical year numbering, the year 1 BCE becomes 0, the year 2 BCE becomes -1, and in general any given year n BCE becomes -(n-1). Years CE are identical. The system is so named due to its original use by astronomers. (However, note that astronomers mostly find it convenient to use
Julian dates.)