Determination of the day of the week day of the week begins by starting from an ‘anchor date’: a known pair (such as January 1, 1800 as a Wednesday), determining the number of days between the known day and the day that you are trying to determine, and using arithmetic modulo 7 to find a new numerical day of the week. One standard approach is to look up (or calculate, using a known rule) the value of the first day of the week of a given century, look up (or calculate, using a method of congruence) an adjustment for the month, calculate the number of leap years
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),