Learn about cusps
Three explainers that move from the folklore to the physics.
What is a cusp in astrology?
In astrology a cusp is the boundary where one zodiac sign ends and the next begins. People born within a few days of that boundary are often described as "born on the cusp". Because the Sun's entry into each sign shifts by about a day from year to year, your exact sun sign near a boundary depends on your birth year, time, and place.
The twelve cusps and their nicknames
There are twelve cusps, one at each boundary between zodiac signs. Popular astrology gives each a nickname, such as the Cusp of Power (Aries-Taurus) or the Cusp of Magic (Gemini-Cancer), and describes cusp-born people as blending the two neighbouring signs. These descriptions are folklore rather than evidence-based.
The sky versus the zodiac
Western astrology's twelve signs are equal 30-degree slices of the sky tied to the seasons, not the constellations they are named after. Because Earth's axis slowly wobbles (precession), the signs and constellations have drifted roughly a month apart over two thousand years. Controlled studies have not found that signs predict personality.
Ready to check a birthday? Use the cusp finder.