Planets in Signs
The second decan of Aquarius runs 10 to 20 degrees, roughly January 30 to February 8, ruled by Mercury. What a decan is, where the idea came from, and the tarot card that shares these ten degrees.
The Sun covers about a degree a day, so a decan takes roughly ten days. These are the calendar dates the Sun spends in the second decan of Aquarius, computed across 1930 to 2035.
| Degrees | 10 to 20 of Aquarius |
| Dates | January 30 to February 8 |
| Length | 10 days |
| Ruler | Mercury |
| Sign ruler | Uranus and Saturn |
| Tarot card | Six of Swords |
The first and last days shift a little between years, because the Earth's year is 365.2422 days rather than 365 and the whole zodiac drifts about six hours a year against the calendar. January 30 and February 8 are the edges, and both have their own page with the exact figures.
A decan is a third of a sign: ten degrees out of thirty, which the Sun crosses in about ten days. Twelve signs give thirty-six of them, and each one carries its own planetary ruler on top of the sign's. That makes a decan roughly three times more specific than a Sun sign while still needing nothing but a birth date.
The idea is older than the zodiac it now divides. The Egyptians used thirty-six groups of stars, each rising about forty minutes after the last, to tell the time at night. Ten of them were visible across a night, which is one of the threads that led to the day being divided into twenty-four hours rather than some rounder number. The decans were on coffin lids and temple ceilings a long time before anybody attached planets to them.
The planetary rulers came later, from Hellenistic astrology, and they run in what is called the Chaldean order: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon, which is the planets ranked by apparent speed from slowest to fastest. Starting at the first ten degrees of Aries and counting that sequence forward one decan at a time gives every decan its ruler, and it comes out the same every time because it is arithmetic rather than opinion.
Aquarius is Air and Fixed, ruled by Uranus and Saturn, and the traits usually attached to it are independent, inventive, principled, detached and humane. Every Aquarius has that. What the second decan adds is Mercury, and the result is a Aquarius who runs more verbal and more restless.
In practice the pairing shows as thinking it through out loud. A Aquarius from this decan is recognisably Aquarius, with quickness, analysis and a running commentary laid over the top. Compared with the other two thirds of the sign it is the Mercury version, and the difference is usually obvious once you know to look for it.
| Decan | Degrees | Ruler | What it adds |
|---|---|---|---|
| First | 0 to 10 | Venus | charm, ease and an eye for what is pleasant |
| Second (this one) | 10 to 20 | Mercury | quickness, analysis and a running commentary |
| Third | 20 to 30 | Moon | feeling, memory and an instinct for what people need |
That table is the argument for decans in one block. Three people can all be Aquarius and be running it through Venus, Mercury and Moon, which is a genuine difference and one a Sun sign on its own throws away.
The standard English tarot deck was built on this same system. Every pip card from Two to Ten corresponds to one decan, which means the second decan of Aquarius and the Six of Swords are two descriptions of one ten-degree stretch of sky.
That correspondence is not decoration and it is not something the tarot borrowed loosely. The Rider deck of 1909 was drawn to a scheme in which the thirty-six pips map onto the thirty-six decans in order, and the card's traditional meaning was derived from the decan's ruler and sign rather than the other way round. Reading the card is another way of reading these ten degrees, and it is frequently the more vivid one.
Mercury in Aquarius is the third description of the same thing, this time as a birth chart placement.
Your Sun is in this decan, which narrows it from one sign in twelve to one stretch in thirty-six. Worth doing something with: read the Mercury pages as well as the Aquarius ones, because half of what is usually described as your sign is being coloured by a planet most descriptions never mention.
The full account of the Sun in Aquarius is here, and Aquarius season covers the whole stretch of the year.
A decan is the Sun, more precisely. The Moon, the rising sign and the houses all need a birth time, and they are where most of what people actually recognise about themselves lives. If you do not know your birth time, this covers how to find it.
Roughly January 30 to February 8, which is 10 to 20 degrees of Aquarius. The edges move by a day either way between years.
Mercury, from the Chaldean order counting forward from the first decan of Aries. Aquarius itself is ruled by Uranus and Saturn.
The Six of Swords. Every pip card from Two to Ten corresponds to one decan, and this is the one.
By your birth date, and more precisely by your Sun's degree. The first ten degrees of a sign are the first decan, ten to twenty the second, twenty to thirty the third.
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Astrology CalendarNine retrogrades, five eclipses, twenty-five lunations and exactly one planet changing sign. Every date and degree below was computed from an ephemeris rather than copied, and this page says when.
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