December 21 at a glance
- Zodiac sign
- ♐ Sagittarius
- Element and modality
- fire, mutable
- Ruling planet
- Jupiter
- Place in the sign
- Day 30 of Sagittarius; Capricorn starts 1 day later on the calendar
- Decan
- 3 of 3, ruled by Leo (December 12 to 21)
- Cusp
- Sagittarius to Capricorn
- Birthday number
- 21 reduces to 3 (2 + 1 = 3)
- December birthstone
- Turquoise, also Tanzanite, Zircon, Blue Topaz
Ask about the zodiac sign for December 21
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The shortest day of the northern year
The December solstice is the moment the Sun stands over the Tropic of Capricorn, 270 degrees along the ecliptic. Astrology marks it as 0 degrees of Capricorn, so the longest night north of the equator and the first moment of the sign are the same event. South of the equator the same moment brings the longest day and the start of summer.
The night of December 20 and 21 is the Iranian festival of Yalda, kept in the dark hours of the solstice with fruit, poetry and staying awake until dawn. Capricorn's reputation for endurance is often tied to this dark point of the year, an association astrologers draw rather than a fact about the sign, which is only a division of the Sun's path.
Is December 21 a cusp date?
The standard table gives December 21 as the last day of Sagittarius, a mutable fire sign. In the years when the solstice falls on this date in UTC, births that follow it are Capricorn instead, a cardinal earth sign, and the shift is a real change of sign and element, not a shade. For this date the clock matters more than for most others.
The standard table gives Sagittarius. The change from Sagittarius into Capricorn can reach December 21 in some year and time zone within 2000 to 2050, so a birth on this date can belong to either sign.
Across 2000 to 2050 (51 years) the Sun entered Capricorn on these UTC dates: December 21 in 39, December 22 in 12.
Within those years the entry into Capricorn fell on December 21 between 05:00 and 00:00 UTC; on December 22 between 00:20 and 07:00 UTC. Clocks in populated time zones run from UTC-10 to UTC+12, so the same instant can read as the day before or the day after, and your birth time and birth place decide which side of it you were born.
| Year | Sun enters Capricorn |
|---|---|
| 2026 | about Dec 21, 20:50 UTC |
| 2027 | about Dec 22, 02:40 UTC |
| 2028 | about Dec 21, 08:30 UTC |
Born near that moment? The sun sign calculator takes your year, time and time zone.
The Sagittarius decan for December 21
December 21 falls in decan 3 of Sagittarius, December 12 to 21, ruled by Leo. Each sign is cut into three decans of about ten days, ruled in turn by the sign itself and the next two signs of its element.
Leo, a fire sign, rules the third Sagittarius decan. Tradition describes the stretch as the warmest and most expressive of the three, with a stage-ready streak that the archer alone does not suggest. A Capricorn birth on the same day has the first decan of its sign instead.
Birthday number 3 for December 21
The day 21 reduces to 3: 2 + 1 = 3. No step lands on a master number.
A 21 reduces to 3. The date written as 12/21 reads the same mirrored, a rare number pattern, and numerologists like symmetrical dates. Threes are tied to expression and to the socialising that midwinter encourages, and the 21 echoes the closing card of the Major Arcana, The World, a picture of a cycle ending.
The December birthstone
Birthstones follow the month and not the day, so a birthday on December 21 shares Turquoise (also Tanzanite, Zircon, Blue Topaz) with every other December birthday. See December birthstones.
December 21 zodiac questions
Is December 21 the end of Sagittarius or the start of Capricorn?
Sagittarius on the usual calendar, and Capricorn when the solstice came before your birth moment. The ingress table shows the UTC dates the Sun has entered Capricorn, and the sun sign calculator uses your own year and time.
Is the winter solstice always on December 21?
No. It falls on December 21 or 22 in UTC depending on the year, and on clocks in the far east a December 21 moment in UTC can already read December 22. The page prints the next three solstice times from our ephemeris.
What separates a December 21 birth from a December 22 one?
On the calendar the 21st is the last Sagittarius day and the 22nd the first Capricorn day, though the solstice moment can put either date on either side of the line.
Dates next to December 21
Other December dates with their own page: December 22.
A birthday date is one piece of the chart
Our astrologers read the Moon, rising sign, houses and transits that a date cannot show.
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