Gemini Dates, Traits & Compatibility (May 21 to Jun 20)

Gemini illustration

Gemini runs May 21 to June 20, and it’s the one sign whose two brightest stars are named after actual mythological brothers who couldn’t stand the idea of being permanently separated.

Dates, element, and modality

• Dates: May 21 to June 20 (inclusive)
• Element: Air
• Modality: Mutable
• Symbol: The Twins, drawn as two vertical parallel lines (♊)

Mutable signs sit at the tail end of a season, the transitional stretch where one set of conditions is giving way to the next, and Gemini closes out spring right as summer approaches. That transitional placement is exactly where astrology gets its “adaptable, always mid-conversation” read on the sign.

The myth behind the symbol

Gemini’s twins are Castor and Pollux, sons of Leda, queen of Sparta, but with two different fathers: Castor’s father was Tyndareus, Leda’s mortal husband, while Pollux’s father was Zeus. That split parentage meant Castor was mortal and Pollux wasn’t. When Castor died, Pollux couldn’t accept living forever without his brother, so he asked Zeus to let them share his immortality instead. Zeus agreed and set them both among the stars, which is why Gemini’s two brightest stars carry their names to this day: Castor and Pollux, appropriately inseparable even now. Ancient Babylonian astronomy had already paired the same two stars as “the Great Twins” long before the Greeks attached this particular story to them.

Ruling planet

Gemini is traditionally ruled by Mercury, astrology’s planet of communication and quick thinking, a fitting pair for a Mutable Air sign built around movement between ideas. As with every sign here, that’s a symbolic astrology assignment, not a physical fact: Mercury doesn’t sit inside the constellation Gemini or exert any special orbital influence on it. The rulership system is inherited chart shorthand, useful for reading a horoscope, not a claim about the solar system.

Personality lore

Mutable Air combines two traits that reinforce each other: Air’s focus on ideas and conversation, and Mutable’s comfort with change. Popular astrology leans on that combination to describe Gemini as curious, quick in conversation, and drawn to variety over routine, in contrast to Fixed Air sign Aquarius, which gets cast as more stubbornly independent, or Cardinal Air sign Libra, framed as the initiator of social connection. The “two-sided” reputation many people associate with Gemini traces directly back to the twins in its symbol and myth, not just a coincidence of naming.

Compatibility

Charts commonly pair Gemini with Libra and Aquarius, the other two Air signs, on the idea that shared-element signs process the world the same way, through ideas and conversation rather than instinct or sensation. Fire signs, especially Aries and Leo, are the other classic match, since Air is said to feed Fire the oxygen it needs to keep burning. Treat any compatibility list as folklore rather than a verdict on real relationships.

Tropical zodiac vs the night sky

Gemini’s dates follow the tropical zodiac, a seasonal calendar system rather than a live map of the stars. Worth stating plainly, once: none of this is science. Astronomy describes the actual, measurable positions of stars and planets; astrology layers cultural meaning onto a birth date using a much older symbolic framework, and conflating the two muddies both. Precession, the slow 26,000-year wobble of Earth’s axis, has shifted which constellation is actually behind the sun on any given date since these tropical boundaries were set in antiquity. NASA’s explainers on this topic also flag Ophiuchus, a 13th constellation the ecliptic passes through that tropical astrology never turned into a sign. If you were born right at the edges of this window, the neighboring Taurus page is worth a look, since some charts nudge the cusp by a day.

Nearby signs

Compare Taurus and Cancer, or browse the full Western zodiac hub. Gemini birthdays span two birthstone months, May and June, a separate tradition from sun signs.

Enter your birth date in the birthday calculator to confirm your sign, weekday, and moon phase, and see methodology for how this site classifies dates.