What is a Decanate?
Each astrological sign is divided into three parts, and each part is called a decanate or a decan, the terms are used interchangeably.
The word comes from the Greek word dekanoi, meaning ten days apart. The Greeks took their word from the Egyptians, who divided their year into 360 days. The Egyptian year had twelve months of thirty days each, and each month was further divided into three sections of ten days each. It was these ten-day sections the Greeks called dekanoi.
Astrology still divides the zodiac into decanates. There are twelve signs in the zodiac, and each sign is divided into three decanates. You might picture each decanate as a room. You were born in a certain sign, for example, Gemini, that consists of three rooms (decanates). Which room of Gemini were you born in?
The zodiac is a 360-degree circle. Each decanate isten degrees of that circle, or about ten days long, since the Sun moves through the zodiac at approximately the rate of one degree per day. (This is not exact because not all of our months contain thirty days.)
The decanate of a sign does not change the basic characteristics of that sign, but it does refine and individualize the sign’s general characteristics. For example, if you were born in the second decanate of Gemini, that does not change the fact that you are Geminian. It does indicate that you have somewhat different and special characteristics from those Geminians born in the first decanate or the third decanate.
Each decanate has a constellation in the heavens that represents it. These constellations have special mystical meanings that also add to the unique quality of your decanate.
Finally, each decanate has a specific planetary ruler, sometimes called a subruler because it does not usurp the overall rulership of the sign. The subruler can only enhance, or add to, the distinct characteristics of that decanate. For example, the entire sign of Gemini is ruled by Mercury, but the second decanate of Gemini is sub-ruled by Venus. The influence of Venus, the subruler, combines with the overall authority of Mercury to make the second decanate of Gemini unlike any other in the zodiac. In the following guide, I have outlined the subtle differences and special characteristics of your own unique decanate.