The Twins · May 21 – June 20
May 21 Zodiac Sign
Born on May 21, you're usually a Gemini, on the Taurus–Gemini cusp — curious, witty and endlessly adaptable — the zodiac's great communicator.
Zodiac sign
Element · Modality
Air · Mutable
Decan (first)
Jupiter-ruled
Birthstone
Emerald
Birth flower
Lily of the valley
Season position
Day 1 of 31
What astrology says about a May 21 birthday
May 21 is day 1 of Gemini season, so astrologers link it with the sign's core character: curious, witty, adaptable, social. Traits astrologers commonly associate with Gemini include excellent communicator and storyteller; adaptable and comfortable with change; social, friendly and easy to talk to.
A commonly cited growth area for Gemini: inconsistency or changing plans often. For the full picture of the sign, read the Gemini guide.
1st decan of Gemini: Jupiter
Each sign is divided into three decans, 10° slices that the Sun crosses in about ten days each. May 21 falls in the first decan of Gemini (about May 21–30), which the traditional Chaldean system assigns to Jupiter. Astrologers say that adds optimism, generosity and big-picture thinking.
Jupiter widens the sign's horizons, adding faith in the future, a generous streak and an appetite for growth, travel and learning.
A Taurus–Gemini cusp birthday
May 21 is the first day of Gemini season, right beside Taurus. It is often said that people born this close to a boundary show traits of both signs: Taurus's grounded and reliable alongside Gemini's curious and witty.
Astrology doesn't recognise a blended sign, and the exact moment the Sun changes signs shifts from year to year. Only a chart calculated from your birth year, time and place can confirm which side of the line you were born on.
The number 21 in numerology
The 21 is tied to sociability and self-expression. Birthdays on the 21st are read as charismatic, optimistic and at ease in a crowd.
Numerology is a separate tradition from astrology and is offered here for interest.
May birthstone and flower
The modern birthstone for May is Emerald and the commonly listed birth flower is the lily of the valley. May falls in late spring in the north and late autumn in the south.
Gemini love and compatibility
For Gemini, attraction starts in the mind. They fall for good conversation, clever banter and someone who can keep up with their many interests. Variety, spontaneity and shared curiosity keep a relationship alive.
Astrology is a symbolic tradition, not a science, and interpretations vary between astrologers. This page is for reflection and entertainment, not prediction or advice.
Beyond your May 21 Sun sign
Your Gemini Sun is one planet. Your Moon, Rising sign and the exact Jupiter-ruled decan details live in your full natal chart. Get yours free on Skygram.
Get my free birth chartMay 21 birthday FAQ
What zodiac sign is May 21?
May 21 falls in Gemini, which runs from May 21 to June 20 in the tropical zodiac. The Sun changes sign at a slightly different moment each year, so the boundary can fall a day or so either side of these dates. If you were born close to the edge, your birth year, time and place decide it.
Is May 21 a cusp birthday?
Yes. May 21 sits within a day or two of the Taurus–Gemini boundary, and it is often said that people born this close to a boundary show traits of both signs. Astrologers still assign the Sun to one sign, and only a birth chart calculated from your birth year, time and place shows which.
Which decan is May 21?
May 21 is in the first decan of Gemini (May 21–30). In the traditional Chaldean system this decan is ruled by Jupiter, which astrologers say adds its own flavour to Gemini. Some modern astrologers assign decan rulers by element instead, which gives different planets, and decans are strictly 10° slices of the zodiac, so the date range is approximate.
What are the birthstone and flower for May?
The modern birthstone for May is Emerald and the birth flower is the lily of the valley. These come from calendar tradition rather than astrology, and the lists vary by country and source.