It is also called Jaláli. The Persian Era was used at that period. Through the interruption of continuity in intercalation, the commencements of the years fell into confusion. At the instance of Sulṭán Jalálu'ddin* Malik Sháh Saljúki, Omar Khayyam and several other learned men instituted this era. The beginning of the year was determined from the sun's entry into Aries. The years and months were at first Natural, but now the month is the ordinary Artificial. Each month consists of 30 days and at the end of Isfandármuz, they add 5 or 6 days. Of this era, 516 years have elapsed.