Nisan-years is an ancient calendar system used around Mesopotamia. Its area of usage covers Elam, Persia, Media, Syria and Israel/Judea. Its beginning was from prehistorical era. Ever since Mesopotamia had historical writings, even before the Old Babylonian Empire of Hammurabi, its calendar used the Nisan-years. Nisan-years is often called the Jewish Religious Calendar, in contrast to Tishri-years, which is often called the Jewish Civil Calendar.