Whose Day Is This?

For convenience, the month was usually subdivided into smaller time periods. The Greeks divided the month into three periods of ten days, but a division

of seven days was older and more common in the Near East. We find the seven-day week already in Genesis.

The names that we assign to the days have their origin in the division of the day into 24 hours, which originated in Egypt. In the Hellenistic period (300 B.C.E. - 100 B.C.E.) it became common to assign a ruling planet (including the Sun and Moon) to each hour of the day. The common order of the wandering heavenly bodies was Saturn-Jupiter-Mars-Sun-Venus-Mercury-Moon. The first hour of the first day was assigned to the Sun, the second to Venus, the third to Mercury, etc., repeating the cycle in the order given above. The 24th hour was thus assigned to Mercury and the first hour of the second day to the Moon.

Naming the days after the planets that rule their first hours, we thus arrive at the sequence Sun's day-Moon's day-Mars's day-Mercury's day-Jupiter's day-Venus's day-Saturn's day.

The modern English variations on these names are due to substituting Nordic or Saxon gods for some of the Roman names: Tiw for Mars, Wotan for Mercury, Thor for Jupiter, Frigg for Venus.