366366 366 Year 366 (CCCLXVI) was a common year starting on Sunday of the Julian calendar. At the time, it was known as the Year of the Consulship of Gratianus and Dagalaifus (or, less frequently, year 1119 "Ab urbe condita"). The denomination 366 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years. Events. <onlyinclude> </onlyinclude> 366 Year 366 (CCCLXVI) was a common year starting on Sunday of the Julian calendar. At the time, it was known as the Year of