The dates printed beside each sign are a convention. The Sun crosses from Taurus into Gemini at one exact moment, and that moment moves: about six hours later each year, then back a day in leap years. So on May 21 the answer depends on the year, and in some years on the hour.
Sign by birth date
What zodiac sign is May 21?
May 21 sits on the line between Taurus and Gemini: the year and the hour of birth decide which. The usual table counts this day in Gemini.
Sun signTaurus / Gemini
The sign runsMay 21 – June 20
ElementAir
ModalityMutable
Ruling planetMercury
Decanfirst, under Mercury
Day in the sign1 of 31
Persian calendar31 Ordibehesht, in most years
Between Taurus and Gemini: the year decides
The Sun enters Gemini during the day in (time in UTC):
1940 (05:26), 1941 (11:16), 1942 (17:07), 1943 (22:57), 1944 (04:47), 1945 (10:36), 1946 (16:24), 1947 (22:12), 1948 (03:58), 1949 (09:44), 1950 (15:30), 1951 (21:16), 1952 (03:02), 1953 (08:49), 1954 (14:36), 1955 (20:23), 1956 (02:12), 1957 (08:02), 1958 (13:52), 1959 (19:42), 1960 (01:33), 1961 (07:23), 1962 (13:13), 1963 (19:03), 1964 (00:51), 1965 (06:39), 1966 (12:26), 1967 (18:13), 1969 (05:45), 1970 (11:31), 1971 (17:17), 1973 (04:51), 1974 (10:39), 1975 (16:28), 1977 (04:08), 1978 (09:58), 1979 (15:49), 1981 (03:29), 1982 (09:18), 1983 (15:07), 1985 (02:41), 1986 (08:28), 1987 (14:14), 1989 (01:45), 1990 (07:32), 1991 (13:19), 1993 (00:55), 1994 (06:44), 1995 (12:34), 1997 (00:15), 1998 (06:05), 1999 (11:56), 2002 (05:22), 2003 (11:10), 2006 (04:28), 2007 (10:14), 2010 (03:34), 2011 (09:22), 2014 (02:50), 2015 (08:41), 2018 (02:12), 2019 (08:01), 2022 (01:25), 2023 (07:11), 2026 (00:29), 2027 (06:15)
The whole day is Gemini in:
1968, 1972, 1976, 1980, 1984, 1988, 1992, 1996, 2000, 2001, 2004, 2005, 2008, 2009, 2012, 2013, 2016, 2017, 2020, 2021, 2024, 2025, 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: Gemini
Gemini is mutable air under Mercury: the sign of the messenger. Its natives think in pairs, speak easily, learn fast and tire of anything that stands still. They are the ones who carry news between rooms and ideas between people. Their gift is the quick connection; their task is to stay with one thing until it deepens.
The first decan, and what it changes
The first decan is Mercury twice over: the purest Gemini. Thought and speech are quick as light, curiosity has no limit, and two things are always being done at once. Nothing is harder for these natives than silence.
The sign: Taurus
Taurus is fixed earth, the sign of what lasts. Venus rules it, so its natives are builders with taste: patient, loyal, hard to hurry, and at home wherever there is good bread, good cloth and a promise kept. They hold on, to people and to positions alike, and their strength is the calm that others lean on.
The third decan, and what it changes
The third decan is Saturn's, through Capricorn. Ambition joins endurance: these natives build for the long term, carry responsibility early, and are the most disciplined and the most serious of the Taurus born.
In short
What zodiac sign is May 21?
Taurus or Gemini, 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 May 21?
The first decan of Gemini, governed by Mercury.
What are the element and ruling planet of Gemini?
Gemini is a Mutable Air sign ruled by Mercury.