December 21 Zodiac Sign: Sagittarius or Capricorn?

December 21 is Sagittarius on the dates most calendars use, but it is a boundary day: from 1950 to 2029, about 74 percent of December 21 birth hours in US Eastern time fell in Sagittarius and about 26 percent in Capricorn.

Check a December 21 Sagittarius against any sign

You were born on a boundary day. The exact changeover shifts by up to a day depending on the year and the time of birth, so both signs are shown.

Share of December 21 birth hours, 1950 to 2029, US Eastern time
Sign	Share	The Sun's degrees
Sagittarius	74 percent	28.5 to 30.0 degrees of Sagittarius
Capricorn	26 percent	0.0 to 0.9 degrees of Capricorn

The Sun's move into Capricorn landed between December 21 and December 22 (US Eastern time) in those years; the tropical year is about 365.24 days, so the moment shifts by hours from year to year and moves back after each leap day.

Check a December 21 birth by year and time

December 21 zodiac compatibility

If you are a Sagittarius

By this site's zodiac points method, a December 21 Sagittarius scores highest with Aries and Leo, a strong match at 8 of 8 points, then Libra and Aquarius, a good match at 5 of 8.

Pair	Verdict	Points	Aspect
Aries and Sagittarius	strong match	8 of 8	trine
Leo and Sagittarius	strong match	8 of 8	trine
Libra and Sagittarius	good match	5 of 8	sextile
Sagittarius and Aquarius	good match	5 of 8	sextile

who a December 21 Sagittarius is compatible with

Today's Sagittarius love horoscope

If you are a Capricorn

By this site's zodiac points method, a December 21 Capricorn scores highest with Taurus and Virgo, a strong match at 8 of 8 points, then Scorpio and Pisces, a good match at 5 of 8.

Pair	Verdict	Points	Aspect
Taurus and Capricorn	strong match	8 of 8	trine
Virgo and Capricorn	strong match	8 of 8	trine
Scorpio and Capricorn	good match	5 of 8	sextile
Capricorn and Pisces	good match	5 of 8	sextile

who a December 21 Capricorn is compatible with

Today's Capricorn love horoscope

Have your partner's birthday? Compare December 21 with your partner's birthday.

Scores come from this site's zodiac points method (formula 1.1), reviewed by Jahben R., astrologer, on 2026-09-23. How it works is on the methodology page.

Sagittarius at a glance for a December 21 birthday

If you are a Sagittarius

Element: fire
Modality: mutable
Ruler: Jupiter
Position: day 30 of 30 of Sagittarius
Next sign: Capricorn, from December 22

If you are a Capricorn

Element: earth
Modality: cardinal
Ruler: Saturn
Position: the day before Capricorn's first day on most calendars (December 22)
Next sign: Aquarius, from January 20

December 21 decan (Tradition)

In the triplicity system of decans, a tradition, December 21 falls at the end of the third decan of Sagittarius (20 to 30 degrees), ruled by the Sun, or the start of the first decan of Capricorn (0 to 10 degrees), ruled by Saturn, depending on the year and hour.

The older Chaldean system of decans assigns different rulers.

Famous people born on December 21

Emmanuel Macron, politician, born 1977
Hu Jintao, politician, born 1942
Jane Fonda, actor, born 1937
Heinrich Böll, writer, born 1917
Frank Zappa, composer, born 1940

Birth dates from Wikidata (CC0), fetched 2026-09-26.

A note on December 21 birthdays

A cusp date on most calendars, December 21 keeps roughly 74 percent of itself in Sagittarius, sitting at 28.5 to 30.0 degrees, while about 26 percent already opens into Capricorn, at 0.0 to 0.9 degrees, the day before Capricorn's first day on most calendars. Aries or Leo paired with Sagittarius scores a strong match at 8 in this site's own reckoning, and Taurus or Virgo paired with Capricorn scores the same way. The tradition reads Sagittarius as needing room and honesty and Capricorn as needing steadiness, so a cusp partner may carry either pull, toward openness or toward a plan.

Questions people ask

Is December 21 a Sagittarius or a Capricorn?

Either, depending on the birth. On the dates most calendars use, December 21 is Sagittarius. From 1950 to 2029, about 74 percent of December 21 birth hours in US Eastern time fell in Sagittarius and about 26 percent in Capricorn; the year, the hour and the time zone decide.

Is December 21 on the Sagittarius and Capricorn cusp?

The Sun changes sign on or around December 21, so the day can belong to Sagittarius or Capricorn. A cusp is not a thirteenth sign in Western astrology or in this site's scoring: a December 21 birth is one sign or the other.

Who is a December 21 Sagittarius or Capricorn most compatible with?

By this site's zodiac points method, a Sagittarius scores highest with Aries and Leo (a strong match, 8 of 8 points), then Libra and Aquarius (a good match, 5 of 8); a Capricorn with Taurus and Virgo (a strong match, 8 of 8 points), then Scorpio and Pisces (a good match, 5 of 8).

Does the birth year change the zodiac sign for December 21?

Yes. The Sun's move into Capricorn landed between December 21 and December 22 (US Eastern time) from 1950 to 2029, so the year, the hour and the time zone decide a December 21 sign. The calculator on the zodiac sign dates page checks one birth.

Birthdays around December 21

December 20, Sagittarius
December 22, Sagittarius or Capricorn
All December birthdays

Sources

astronomy-engine 2.1.19: the Sun's position; the methodology page records its check against NASA JPL Horizons, and the build checks it against published equinox and solstice times
This site's zodiac points method: formula 1.1
Wikidata (CC0): birth dates, fetched 2026-09-26