Tradition

March 21 Zodiac Sign

Tradition: Western astrology. A tradition, not a forecast. Astrologers read it this way; the evidence does not.

By Suraj Giri

March 21 is Aries on the dates most calendars use, but it is a boundary day: from 1950 to 2029, about 99 percent of March 21 birth hours in US Eastern time fell in Aries and about 1 percent in Pisces.

Check a March 21 Aries 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 March 21 birth hours, 1950 to 2029, US Eastern time
SignShareThe Sun's degrees
Aries99 percent0.0 to 2.1 degrees of Aries
Pisces1 percent29.8 to 30.0 degrees of Pisces

The Sun's move into Aries landed between March 19 and March 21 (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 March 21 birth by year and time

March 21 zodiac compatibility

If you are an Aries

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

PairVerdictPointsAspect
Aries and Leostrong match8 of 8trine
Aries and Sagittariusstrong match8 of 8trine
Aries and Geminigood match5 of 8sextile
Aries and Aquariusgood match5 of 8sextile

who a March 21 Aries is compatible with

Today's Aries love horoscope

If you are a Pisces

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

PairVerdictPointsAspect
Cancer and Piscesstrong match8 of 8trine
Scorpio and Piscesstrong match8 of 8trine
Taurus and Piscesgood match5 of 8sextile
Capricorn and Piscesgood match5 of 8sextile

who a March 21 Pisces is compatible with

Today's Pisces love horoscope

Have your partner's birthday? Compare March 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.

Aries at a glance for a March 21 birthday

If you are an Aries

  • Element: fire
  • Modality: cardinal
  • Ruler: Mars
  • Position: day 1 of 30 of Aries
  • Next sign: Taurus, from April 20

If you are a Pisces

  • Element: water
  • Modality: mutable
  • Ruler: Neptune (traditionally Jupiter)
  • Position: the day after Pisces' last day on most calendars (March 20)
  • Next sign: Aries, from March 21

March 21 decan (Tradition)

In the triplicity system of decans, a tradition, March 21 falls at the end of the third decan of Pisces (20 to 30 degrees), ruled by Pluto (traditionally Mars), or the start of the first decan of Aries (0 to 10 degrees), ruled by Mars, depending on the year and hour.

The older Chaldean system of decans assigns different rulers.

Famous people born on March 21

  • Ronaldinho, footballer, born 1980
  • Gary Oldman, actor, born 1958
  • Sergey Lavrov, diplomat, born 1950
  • Antoine Griezmann, footballer, born 1991
  • Slavoj Žižek, philosopher, born 1949

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

A note on March 21 birthdays

A cusp date, March 21 carries 99 percent Aries and just 1 percent Pisces, the tail end of a sign that closed the day before, March 20. The Aries share opens the sign at day 1 of 30, 0.0 to 2.1 degrees, while the Pisces sliver sits at 29.8 to 30.0 degrees, the day after Pisces' last day on most calendars. By this site's points method, Aries takes a strong match of 8 with Leo and with Sagittarius, a trine astrologers read as easiest, and a good match of 5 with Gemini and with Aquarius, a friendlier sextile.

Questions people ask

Is March 21 an Aries or a Pisces?
Either, depending on the birth. On the dates most calendars use, March 21 is Aries. From 1950 to 2029, about 99 percent of March 21 birth hours in US Eastern time fell in Aries and about 1 percent in Pisces; the year, the hour and the time zone decide.
Is March 21 on the Aries and Pisces cusp?
The Sun changes sign on or around March 21, so the day can belong to Aries or Pisces. A cusp is not a thirteenth sign in Western astrology or in this site's scoring: a March 21 birth is one sign or the other.
Who is a March 21 Aries or Pisces most compatible with?
By this site's zodiac points method, an Aries scores highest with Leo and Sagittarius (a strong match, 8 of 8 points), then Gemini and Aquarius (a good match, 5 of 8); a Pisces with Cancer and Scorpio (a strong match, 8 of 8 points), then Taurus and Capricorn (a good match, 5 of 8).
Does the birth year change the zodiac sign for March 21?
Yes. The Sun's move into Aries landed between March 19 and March 21 (US Eastern time) from 1950 to 2029, so the year, the hour and the time zone decide a March 21 sign. The calculator on the zodiac sign dates page checks one birth.

Birthdays around March 21

Sources