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Decans

Revised 2025-11-08 · Contributors · How entries are written

Each of the twelve signs is divided into three decans of ten degrees, giving thirty-six divisions of the ecliptic. The system is of Egyptian origin, where the decans were originally star groups used for timekeeping at night, and was absorbed into Hellenistic astrology in a modified form.

The two rulership schemes

Chaldean order

Rulership runs in the descending planetary order Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon, repeating continuously from the first decan of Aries.

Produces a sequence unrelated to sign boundaries, which is the point of it.

Triplicity scheme

The three decans of a sign are assigned to the three signs of the same element, in order. The first decan of Aries is ruled by Aries, the second by Leo, the third by Sagittarius.

This is the scheme most often encountered in modern English-language texts.

The two schemes are not reconcilable and produce different rulers for nearly every decan. Sources frequently fail to state which they are using, which is the most common cause of confusion for readers comparing two references.

Use in practice

Decans are used chiefly to differentiate positions within a sign, most often for the Sun. Their use in modern practice is uneven. Some practitioners regard them as a meaningful refinement, others as a needless subdivision of an already broad category, and a third group encounters them only through the seventy-eight-card tarot correspondences, in which thirty-six of the minor arcana map to the decans.