The ancient civil Egyptian calendar had a year that was 360 days long and was divided into 12 months of 30 days each, plus five extra days at the end of the year. The months were divided into three weeks of ten days each. Because the ancient Egyptian year was almost a quarter of a day shorter than the solar year and stellar events therefore "wandered" through the calendar, it has been referred to as the annus vagus, or "wandering year".