The Sea-Goat · December 22 – January 19
December 31 Zodiac Sign
Born on December 31, you're a Capricorn — disciplined, ambitious and patient — the zodiac's master strategist.
Zodiac sign
Element · Modality
Earth · Cardinal
Decan (first)
Jupiter-ruled
Birthstone
Turquoise
Birth flower
Narcissus
Season position
Day 10 of 29
What astrology says about a December 31 birthday
December 31 is day 10 of Capricorn season, so astrologers link it with the sign's core character: ambitious, disciplined, responsible, patient. Traits astrologers commonly associate with Capricorn include ambitious with a strong long-term vision; disciplined and self-motivated; responsible and trustworthy.
A commonly cited growth area for Capricorn: pessimism or excessive caution. For the full picture of the sign, read the Capricorn guide.
1st decan of Capricorn: Jupiter
Each sign is divided into three decans, 10° slices that the Sun crosses in about ten days each. December 31 falls in the first decan of Capricorn (about December 22–31), which the traditional Chaldean system assigns to Jupiter. Astrologers say that adds optimism, generosity and big-picture thinking.
Jupiter widens the sign's horizons, adding faith in the future, a generous streak and an appetite for growth, travel and learning.
The number 31 in numerology
The 31 combines the 3's expressiveness with the 1's initiative. A birthday on the 31st is linked to practical creativity and the drive to turn ideas into results.
Numerology is a separate tradition from astrology and is offered here for interest.
December birthstone and flower
The modern birthstone for December is Turquoise and the commonly listed birth flower is the narcissus. December falls in the month of the December solstice — winter in the northern hemisphere and summer in the southern.
Capricorn love and compatibility
Capricorn approaches love the way they approach everything else: seriously and with the long term in mind. They are not interested in games; they're interested in building a life with someone.
Astrology is a symbolic tradition, not a science, and interpretations vary between astrologers. This page is for reflection and entertainment, not prediction or advice.
Beyond your December 31 Sun sign
Your Capricorn Sun is one planet. Your Moon, Rising sign and the exact Jupiter-ruled decan details live in your full natal chart. Get yours free on Skygram.
Get my free birth chartDecember 31 birthday FAQ
What zodiac sign is December 31?
December 31 falls in Capricorn, which runs from December 22 to January 19 in the tropical zodiac. The Sun changes sign at a slightly different moment each year, so the boundary can fall a day or so either side of these dates. If you were born close to the edge, your birth year, time and place decide it.
Is December 31 a cusp birthday?
Not by the usual definition, which counts the first and last couple of days of a sign. December 31 is day 10 of Capricorn season, so it is normally read as a clear Capricorn birthday.
Which decan is December 31?
December 31 is in the first decan of Capricorn (December 22–31). In the traditional Chaldean system this decan is ruled by Jupiter, which astrologers say adds its own flavour to Capricorn. Some modern astrologers assign decan rulers by element instead, which gives different planets, and decans are strictly 10° slices of the zodiac, so the date range is approximate.
What are the birthstone and flower for December?
The modern birthstone for December is Turquoise and the birth flower is the narcissus. These come from calendar tradition rather than astrology, and the lists vary by country and source.