Planetary Hours - History

History

The astrological order of the days was explained by Vettius Valens and Dio Cassius (and Chaucer gave the same explanation in his Treatise on the Astrolabe). According to these authors, it was a principle of astrology that the heavenly bodies presided, in succession, over the hours of the day. The Ptolemaic system asserts that the order of the heavenly bodies, from the farthest to the closest to the Earth, is: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. (This order was first established by the Greek Stoics.)

In astrological theory, not only the days of the week, but the hours of the day are dominated by the seven luminaries. If the first hour of a day is dominated by Saturn, then the second hour is dominated by Jupiter, the third by Mars, and so on with the Sun, Venus, Mercury, and the moon, so that the sequence of planets repeats every seven hours. Therefore, the twenty-fifth hour, which is the first hour of the following day, is dominated by the Sun; the forty-ninth hour, which is the first hour of the next day, by the Moon. Thus, if a day is labelled by the planet which dominates its first hour, then Saturn's day is followed by the Sun's day, which is followed by the Moon's day, and so forth, as shown below.

According to Vettius Valens, the first hour of the day began at sunset, which follows Greek and Babylonian convention. He also states that the light and dark halves of the day were presided over by the heavenly bodies of the first hour of each half. This is confirmed by a Pompeian graffito which calls 6 February 60 a Sunday, even though by modern reckoning it is a Wednesday. Thus this graffito used the daylight naming convention of Valens whereas the nighttime naming convention of Valens agrees with the modern astrological reckoning, which names the day after the ruler of the first daylight hour.

These two overlapping weeks continued to be used by Alexandrian Christians during the 4th century, but the days in both were simply numbered 1–7. Although names of gods were not used, the week beginning on Wednesday was named in Greek ton theon ( of the gods), as used by the late fourth-century editor of the Easter letters of Bishop Athanasius, and in a table of Easter dates for 311–369 that survives in an Ethiopic copy. These overlapping weeks are still used in the Ethiopic computus. Each of the days of the week beginning on Sunday is called a "Day of John" whereas each of the days of the week beginning on Wednesday is called a "tentyon", a simple transcription of the Greek ton theon.