Determination of the day of the week the day of the week without any calculations. Examples: December is in row F and 26 is in column E, so the letter for the date is C located in row F and column E. 93 (year mod 100) is in row D (year row) and the letter C in the year row is located in column G. 18 ([year/100] in the Gregorian century column) is in row C (century row) and the letter in the century row and column G is B, so the day of the week is Tuesday. October 13 is a F day. The letter F
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),