Unequal Hours

latin: horae inaequales; horae temporales · egyptian: wnwt (Egyptian 'hour' generally — applied to the seasonal-hour scheme) · greek: ὥρα καιρική (hōra kairikē, 'seasonal hour')

Definition

Unequal hours (also called 'seasonal hours' or 'temporal hours') are a time-of-day convention in which day and night each are divided into twelve hours of variable length according to season. The daytime is partitioned into twelve segments between sunrise and sunset; the nighttime into twelve between sunset and sunrise. Each unequal hour is therefore one-twelfth of the actual daylight or nighttime, lengthening or shortening as the year progresses. At the equinoxes day and night are equal and each hour equals sixty modern minutes; in summer the day-hours are long and night-hours short, and the reverse in winter.

In Tradition

Across Egyptian, Hellenistic, Arabic, and traditional Western practice the unequal hour is the default time-of-day convention. Belmonte and Lull document the seasonal-hour scheme as the dominant model across stellar, solar, and water clocks throughout pharaonic and Ptolemaic Egypt. Bonatti's Liber Astronomiae uses unequal hours for the planetary-hours doctrine: the 12 daytime and 12 nighttime planetary hours each occupy one-twelfth of actual daylight or nighttime, with the Lord of the Hour rotating through the Chaldean order.

In Practice

Traditional electional and horary astrologers compute the planetary hour of any moment by first determining whether the Sun is above or below the horizon, dividing the corresponding daylight or nighttime arc into twelve equal segments, and stepping through the Chaldean order from the planet ruling the first hour of daylight (= the planet ruling that day of the week). The unequal-hour convention is essential for any tradition that derives its planetary-hour rulership from the rotation Chaldean sequence: Saturday's first daylight hour is Saturn, Saturn's hour gives way to Jupiter's hour at the start of the next 1/12 segment, and so on. Modern equal-hour astrology (each hour = 1/24 of the calendar day) is a later convention; for working with traditional sources, unequal hours are the historically correct form.

Historical Origin

The seasonal-hour scheme is the native Egyptian default from at least the Middle Kingdom through the Roman period (Belmonte and Lull); rival equal-hour documents (Cairo JE 86637, the Tanis text, the Medînet Madi ostraca) are isolated exceptions. The Hellenistic and Arabic-Persian inheritance preserves the unequal-hour convention for the planetary-hours doctrine; Bonatti's Liber Astronomiae Vol XI Part III Ch XI is the canonical medieval Latin treatment.

Etymology

Origin: Latin. Meaning: From horae ('hours') + inaequales ('unequal') or temporales ('seasonal') — the technical Latin name for variable-length day and night hours..

Further Reading