Each zodiac sign is divided into three decans of 10 degrees, and your decan depends on how far through your Sun sign the Sun had traveled when you were born. As a rough guide, the first ten days or so of a sign are its first decan, the middle ten days the second, and the last ten days the third. The table below gives approximate dates for all 36; the Sun's exact degree on your birth chart settles any doubt.
Astrologers use decans to explain why two people of the same sign can feel so different. Here's how they work, who rules each one, and how much weight to give yours.
Decan dates for all twelve signs
The dates shift by about a day from year to year, and your time zone can move them too. The planet in brackets is the decan's ruler in the common triplicity system, explained below; where two are given, the second is the traditional ruler.
| Sign | First decan (0 to 10°) | Second decan (10 to 20°) | Third decan (20 to 30°) |
|---|---|---|---|
| Aries | Mar 21 to 30 (Mars) | Mar 31 to Apr 9 (Sun) | Apr 10 to 19 (Jupiter) |
| Taurus | Apr 20 to 29 (Venus) | Apr 30 to May 10 (Mercury) | May 11 to 20 (Saturn) |
| Gemini | May 21 to 31 (Mercury) | Jun 1 to 10 (Venus) | Jun 11 to 20 (Uranus, Saturn) |
| Cancer | Jun 21 to Jul 1 (Moon) | Jul 2 to 12 (Pluto, Mars) | Jul 13 to 22 (Neptune, Jupiter) |
| Leo | Jul 23 to Aug 1 (Sun) | Aug 2 to 12 (Jupiter) | Aug 13 to 22 (Mars) |
| Virgo | Aug 23 to Sep 1 (Mercury) | Sep 2 to 12 (Saturn) | Sep 13 to 22 (Venus) |
| Libra | Sep 23 to Oct 2 (Venus) | Oct 3 to 12 (Uranus, Saturn) | Oct 13 to 22 (Mercury) |
| Scorpio | Oct 23 to Nov 1 (Pluto, Mars) | Nov 2 to 11 (Neptune, Jupiter) | Nov 12 to 21 (Moon) |
| Sagittarius | Nov 22 to Dec 1 (Jupiter) | Dec 2 to 11 (Mars) | Dec 12 to 21 (Sun) |
| Capricorn | Dec 22 to 31 (Saturn) | Jan 1 to 9 (Venus) | Jan 10 to 19 (Mercury) |
| Aquarius | Jan 20 to 29 (Uranus, Saturn) | Jan 30 to Feb 8 (Mercury) | Feb 9 to 18 (Venus) |
| Pisces | Feb 19 to 28 (Neptune, Jupiter) | Mar 1 to 10 (Moon) | Mar 11 to 20 (Pluto, Mars) |
If your birthday falls on or next to a boundary in this table, don't guess. Check your Sun's degree.
How to find your decan from your Sun's degree
A free birth chart shows your Sun's sign and degree, for example "Sun 17° 42′ Libra." Then:
- Ignore the minutes. 17° 42′ means 17 degrees and 42 minutes, so you're in the 17th degree.
- Find the band. 0° to 9° 59′ is the first decan, 10° to 19° 59′ the second, 20° to 29° 59′ the third.
- Name the ruler. 17° Libra is the second decan, which takes on Aquarius, so it's ruled by Uranus, with Saturn as the traditional ruler.
So this person is a Libra with an Aquarian streak: still diplomatic and relationship-minded, but more independent and idealistic than a first-decan Libra, who has Venus twice over. The same method works for your Moon or rising sign, as long as you know their degrees.
The rule behind the rulers
The table uses the triplicity system, the most common one in modern Western astrology. It's simple once you see it: each sign's three decans run through the three signs of its own element, in zodiac order, starting with itself.
Take Leo, a fire sign. The fire signs in order from Leo are Leo, Sagittarius and Aries. So Leo's first decan is pure Leo (the Sun), its second borrows from Sagittarius (Jupiter), and its third from Aries (Mars). Virgo, an earth sign, runs Virgo, Capricorn, Taurus: Mercury, Saturn, Venus.
That's why the first decan of any sign is often called the purest or most typical version of it, and the later decans are described as the sign blended with its elemental siblings. For decans of individual signs in more detail, see our guides to August Virgo vs. September Virgo, June Cancer vs. July Cancer and October Scorpio vs. November Scorpio. Our list of the ruling planets of the zodiac signs explains the modern and traditional rulers.
The older Chaldean decans, and the tarot link
There's a second system, older and used in traditional astrology: the Chaldean decans, also called faces. It assigns the seven classical planets in a fixed repeating order (Mars, Sun, Venus, Mercury, Moon, Saturn, Jupiter, then Mars again) starting from the first decan of Aries. In that scheme, Aries's decans belong to Mars, the Sun and Venus, and Taurus's to Mercury, the Moon and Saturn.
If you've seen a decan list that doesn't match the table above, it's probably this one. It isn't a mistake, just a different tradition.
The Chaldean decans are also the ones behind tarot's numbered minor cards. The Hermetic Order of the Golden Dawn assigned the 36 decans to the 36 cards from Two to Ten in each suit. The Two of Wands, for example, is Mars in the first decan of Aries, and the Three and Four of Wands are the Sun and Venus in Aries's second and third.
Where decans came from
Decans are older than the zodiac signs as we know them. In ancient Egypt, astronomers tracked 36 groups of stars that rose one after another through the year, each taking its turn for about ten days. They used them to tell the hours of the night, and drew them as star tables on the inside of coffin lids.
When Greek-speaking astrologers in Egypt built the horoscopic astrology that became the Western tradition, they folded the decans into the signs: three to a sign, ten degrees each. The planetary rulers came later and developed into the two systems above.
How much a decan changes the picture
A decan is a shading, not a different sign. A third-decan Aries, with Jupiter's influence from Sagittarius, may be more philosophical and travel-hungry than a first-decan Aries, but both are still unmistakably Aries: direct, quick and fond of starting things.
In terms of influence, astrologers would usually rank the decan well below your Moon sign, rising sign and the house and aspects of your Sun. It's best used as a fine-tuning tool when a sign's description almost fits but not quite. If you were born right at the edge of a sign, the question you probably want answered is the one about zodiac cusp signs, which is separate: decans divide the inside of a sign, cusps sit on the border.
Questions readers ask
What decan am I if I was born on the first day of my sign?
The first decan, as long as the Sun had actually entered your sign by the time you were born. If the Sun changed signs on your birthday, check your chart: you may be in the last decan of the previous sign instead.
Which decan is the strongest?
In the triplicity system, the first decan is often called the strongest or purest, because it's ruled by the sign's own planet. That means most typical, not best. Each decan has its own strengths.
Do decans apply to the Moon and rising sign?
Yes. Any point with a sign and degree falls in a decan. Astrologers sometimes read the decan of the rising sign in particular, since it shapes first impressions.
Are decans the same as cusps?
No. A decan is one of three 10-degree sections inside a sign. A cusp is the boundary between two signs. Someone can be in the third decan of a sign without being on its cusp at all.
