Planetary Hours (Elections)

Definition

Planetary hours are a timing system that splits sunrise-to-sunset into twelve equal daytime "hours" and sunset-to-sunrise into twelve equal nighttime "hours" — so each hour's length varies by season and latitude. Each hour is ruled by one of the seven traditional planets in Chaldean order: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. The first hour after sunrise on any weekday is ruled by that day's name-planet — the Sun on Sunday, the Moon on Monday — and the following hours then rotate through Chaldean order.

In Tradition

Across Hellenistic, Arabic-Latin medieval, and modern Western electional practice, planetary hours add a fine timing layer beneath the broader rules. An activity matched to its hour-ruler is read as supported: Venus hours for partnership, art, and reconciliation; Jupiter hours for legal, financial, and expansion matters; Mercury hours for communication and commerce; Mars hours for competition and surgery; Sun hours for matters of authority. Astrologers weigh it differently but agree it supplements the larger framework rather than deciding outcomes.

In Practice

After identifying the activity's planetary signifier, the electional astrologer computes the relevant planetary-hour table for the day and location. Sunrise and sunset times are obtained for the candidate date; the daytime span is divided by twelve, the nighttime span by twelve. The first daytime hour begins at sunrise and is named by the weekday's planet; each subsequent hour cycles backward through Chaldean order (so the Sun-hour on Sunday is followed by Venus, Mercury, Moon, Saturn, Jupiter, Mars, Sun again). Hours matching the activity's significator are preferred. Modern software automates the calculation.

Historical Origin

The Chaldean planetary order and the seven-day weekday cycle are attested in late-Hellenistic and Roman sources (Vettius Valens, Cassius Dio). The fully-developed planetary-hour system is treated in Persian-Arabic sources including al-Biruni's *Tafhim* (1029 CE) and is preserved through medieval Latin works (Bonatti) into early-modern English via William Lilly's *Christian Astrology* (1647; public domain).

Etymology

Origin: Latin/Greek. Meaning: From hora planetaria — hours assigned to the seven wandering stars, in the order established by Chaldean astronomers.

Definition

In Tradition

In Practice

Historical Origin

Etymology

Further Reading