Born on May 21: Zodiac Sign & Birthstone

Anyone born on May 21 is a Gemini. The May 21 birthstone is Emerald and the May 21 birth flower is the Lily of the Valley. This is a boundary date, so in some birth years it falls under Taurus instead.

What it means to be born on May 21

A birthday on the 21st of May falls under Gemini. Gemini is a mutable air sign ruled by Mercury, tied in tradition to communication, curiosity and quick thinking. The twins symbolize its dual, versatile nature. Gemini season bridges spring and the start of summer.

May 21 sits on the Taurus and Gemini boundary

This date is one of the twelve changeovers in the zodiac. A tropical sign begins at the moment the sun reaches a particular point, and that moment drifts by roughly six hours a year before a leap day pulls it back. On a boundary date the crossing can therefore land on either side of the calendar day, depending on the birth year and the time zone. Charts that publish fixed dates, including ours, round it.

In practice that means a birthday on May 21 is Gemini in most years and Taurus in some. Only an ephemeris for the exact birth year and time settles it. The full list of boundaries is in the cusp guide.

What weekday May 21 falls on

A common year is 365 days, which is 52 weeks plus one day, so a birthday moves forward one weekday each year and two across a leap year. Over time it visits all seven. The next time May 21 falls at a weekend is 2028, on a Sunday.

The weekday May 21 falls on over the next ten years.
Year	Weekday	Weekend?
2026	Thursday	no
2027	Friday	no
2028	Sunday	yes
2029	Monday	no
2030	Tuesday	no
2031	Wednesday	no
2032	Friday	no
2033	Saturday	yes
2034	Sunday	yes
2035	Monday	no

Your May 21 birthstone and flower

Because May 21 sits in May, your birthstone is Emerald, a rich green gem traditionally meaning rebirth, love and hope. Your birth flower is the Lily of the Valley, which stands for sweetness, humility and a return of happiness. Together they make a natural birthday pairing for a card, gift or tattoo.

Every tradition tied to May 21

Everything the calendar assigns to May 21, in one table.
Field	Value
Zodiac sign	Gemini (May 21 to June 20)
Element and modality	Mutable Air
Ruling planet	Mercury
Lucky colors	Yellow and Light green
Modern birthstone	Emerald, rich green
Other recognized stones	Chrysoprase (apple green), Agate (banded, many colors)
Birth flower	Lily of the Valley, with Hawthorn as secondary
Day of the year	142 of 366 and 141 of 365
On a sign boundary	yes, shared with Taurus

Gemini strengths and matches

Gemini is often described as adaptable, curious and witty. In the traditional element model, Gemini matches most easily with Libra, Aquarius and Aries. Those percentages come from a published formula you can check on the method page, not from a reading.

See the full birth profile

Want the shareable card for May 21? Open the birth profile tool, pick this date, and download a card to save or share. You can also read the full May overview, or browse every date we cover.

Frequently asked questions

What zodiac sign is May 21?

Anyone born on May 21 is a Gemini, a mutable air sign ruled by Mercury. May 21 sits exactly on the boundary with Taurus, so for some birth years the answer is Taurus instead.

What is the birthstone for May 21?

The birthstone for May 21 is Emerald, the May birthstone, which is rich green. May also recognizes Chrysoprase and Agate.

What is the birth flower for May 21?

The birth flower for May 21 is the Lily of the Valley, the May birth flower, with the Hawthorn as a secondary flower.

What day of the week does May 21 fall on?

In 2026 it falls on a Thursday. Because a common year is 365 days, the weekday moves on by one each year and by two across a leap year, so it cycles through all seven over time. The table on this page lists the next ten years.

Where does May 21 fall in the year?

May 21 is day 142 of a leap year and day 141 of a common year.

Is May 21 on the cusp?

Yes. May 21 is a boundary date between Taurus and Gemini. The sun does not cross the boundary at the same clock time each year, so a birthday here can belong to either sign depending on the birth year and time zone. Settling it needs an ephemeris, not a date table.

Born on May 21