The dates printed beside each sign are a convention. The Sun crosses from Pisces into Aries at one exact moment, and that moment moves: about six hours later each year, then back a day in leap years. So on March 21 the answer depends on the year, and in some years on the hour.
Sign by birth date
What zodiac sign is March 21?
March 21 sits on the line between Pisces and Aries: the year and the hour of birth decide which. The usual table counts this day in Aries.
Sun signPisces / Aries
The sign runsMarch 21 – April 19
ElementFire
ModalityCardinal
Ruling planetMars
Decanfirst, under Mars
Day in the sign1 of 30
Persian calendar1 Farvardin, in most years
Between Pisces and Aries: the year decides
The Sun enters Aries during the day in (time in UTC):
1941 (00:13), 1942 (06:05), 1943 (11:56), 1946 (05:25), 1947 (11:14), 1950 (04:36), 1951 (10:22), 1954 (03:44), 1955 (09:33), 1958 (03:03), 1959 (08:54), 1962 (02:28), 1963 (08:18), 1966 (01:45), 1967 (07:32), 1970 (00:53), 1971 (06:40), 1974 (00:04), 1975 (05:54), 1979 (05:18), 1983 (04:39), 1987 (03:50), 1991 (02:58), 1995 (02:16), 1999 (01:41), 2003 (00:59), 2007 (00:07)
The whole day is Aries in:
1940, 1944, 1945, 1948, 1949, 1952, 1953, 1956, 1957, 1960, 1961, 1964, 1965, 1968, 1969, 1972, 1973, 1976, 1977, 1978, 1980, 1981, 1982, 1984, 1985, 1986, 1988, 1989, 1990, 1992, 1993, 1994, 1996, 1997, 1998, 2000, 2001, 2002, 2004, 2005, 2006, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024, 2025, 2026, 2027, 2028, 2029, 2030
Times are in UTC and exact to about a quarter of an hour; set them against the place and hour of birth. A birth that close to the line is settled by the birth chart, which is computed to the minute. Calculate the birth chart, free
The sign: Aries
Aries opens the zodiac at the spring equinox, and its natives carry that beginning in them. Fire in its first, cardinal form: they start things, say the plain word first, and recover from a fall faster than anyone. Mars gives them courage and a short fuse; their work in life is to finish what they begin.
The first decan, and what it changes
The first decan is Aries undiluted: Mars rules the sign and these ten days as well. The spark is quickest here. Decisions are made on the move, courage comes before calculation, and anger flares and is gone by evening.
The sign: Pisces
Pisces closes the zodiac, mutable water ruled by Jupiter. Its natives take in everything: moods, music, the sorrow of a stranger. They are compassionate, imaginative and hard to pin down, at home in dreams and in prayer. Two fish swim in opposite directions in their sign, and their work is to choose a current without losing their tenderness.
The third decan, and what it changes
The third decan is Mars's, through Scorpio. Under the gentleness there is will: these natives are the most determined of the Pisces born, intense in feeling, and able to go through a hard season and come out whole.
In short
What zodiac sign is March 21?
Pisces or Aries, depending on the year and hour of birth: the Sun changes sign on or next to this day. The table above gives the answer year by year.
Which decan is March 21?
The first decan of Aries, governed by Mars.
What are the element and ruling planet of Aries?
Aries is a Cardinal Fire sign ruled by Mars.