Aracana: The Origin of the Week

Anyone reading this blog is no doubt familiar with the seven day week, but what accounts for the selection and sequence of names ascribed to each day? The sequence of names themselves provides a clue. The day names in English correspond to the Sun, the Moon, the Norse gods Tiu, Woden, Thor and Frigg, and the Roman god Saturn. These correspond to the Roman gods Mars, Mercury, Jupiter and Venus—War, Wind, Thunder and Love—which is why the corresponding day names in Spanish are Martes, Miércoles, Jueves  and Viernes. These particular gods are associated with the five planets [sic] known to antiquity, which the Ptolomeic system arranged in the following order: Saturn, Jupiter, Mars, Sun, Venus, Mercury and Moon (see diagram below).

Hellenistc astrology understood this sequence of planets to rule over the hours of the day, each planet in turn being the head of an hour with the planet ruling the first hour of each day giving its name to that day. Three such cycles is three hours short of 24, which is why the sequence of day names is out of phase with the sequence of planets. Starting with Saturn, three complete cycles plus three planets ends with Mars. The next day will begin with the Sun as head of the first hour, hence Sunday. Starting with the Sun, three complete cycles plus three planets ends with Mercury. The next day will begin with the Moon as head of the first hour, hence Monday, etc.

This astrological week was out of phase with the sabbatical week of the Jews by one day, the Jews regarding Saturday as the seventh day of the week rather than the first. Interestingly enough, both systems associated that day with the god of Time: Saturn to the Romans, Chronos to the Greeks, and El to the Canaanites. The week as we know it in the West today derives from a curious merger of the Hellenistic and Hebrew systems during the age of Constantine the Great, a devote worshiper of the Sun, who understood the Jesus preached by Christians to be an incarnation of the Sun. Romans had not originally observed weekly cycles, though they had observed an informal week based on an eight-day cycle of market days called the nundidae or ‘ninth days’ counting inclusively. Following Constantine's ambiguous embrace of Christianity, the week became established in Rome but with Sunday as the first day of the week.