Determination of the day of the week row C) to find the dominical letter that is E. The letter for September 18 is B, so the day of the week is Thursday. Use 16 (in the Julian century row, column E) and 76 (in row D) to find the dominical letter that is A. February 23 is a "D" day, so the day of the week is Wednesday. In a handwritten note in a collection of astronomical tables, Carl Friedrich Gauss described a method for calculating the day of the week for 1 January in any given year. He never published it. It was finally included in
Names of the days of the week of the week closely parallels that of the Latin system and is ordered after the "Seven Luminaries" (七曜 "qī yào"), which consists of the Sun, Moon and the five planets visible to the naked eye. The Chinese seem to have adopted the seven-day week from the Hellenistic system by the 4th century, although by which route is not entirely clear. It was again transmitted to China in the 8th century by Manichaeans, via the country of Kang (a Central Asian polity near Samarkand). The 4th-century date, according to the "Cihai" encyclopedia, is due to a reference to Fan Ning (範寧/范宁),