This article sheds light upon a “Chinese” calendar described in the Zij-i Ilkhani. In previous studies, some characteristics of the calendar were ascribed to the “Uighurs” However, I will show that it was not originally associated with the Uighur. This “Chinese” calendar was brought to Iran by the Chinese Taoist Fu Mengchi who accompanied his ruler Hulegu. Fu Mengchi informed Nasir al-Din Tusi of the Chinese calendrical system, which Tusi described in his Zij-i Ilkhani. Soon afterward, the calendar was included in the zij of Muhyi al-Din Maghribi, because it was only used among the Mongol ruling class and their Buddhist servants, who were called Uighur. Muhyi al-Din labeled the “Chinese” calendar the “Chinese-Uighur” calendar, and this title was repeated in subsequent zijes. Therefore, modern scholars have regarded the calendar as a product of the Uighurs. However, the title “Uighur” attached to the calendar in later zijes does not reflect the characteristics of the calendar, but rather the circumstances in which it was utilized.