How to use the Zodiac Sign
- Enter your date of birth.
- Read your sun sign with its element and modality.
- Check the cusp note if your birthday falls near a sign boundary.
- Add birth time and place if you want to look up rising and moon signs elsewhere.
How the calculation works
Western astrology uses the tropical zodiac, which divides the year into twelve 30-degree segments starting at the March equinox. Because the tropical year is about 365.2422 days, boundary dates drift by up to a day across the leap-year cycle — which is why someone born on 22 August may be Leo one year and Virgo another. Precise cusp determination needs the birth year and, ideally, the time.
Each sign carries an element — fire, earth, air or water — and a modality: cardinal signs open a season, fixed signs sustain it, mutable signs transition out of it. The sun sign is only one component of a chart; the rising sign depends on birth time and location, and the moon sign changes every two to three days. Sidereal astrology, used in Vedic tradition, accounts for precession and typically places people one sign earlier.
Sign = zodiacal 30° segment containing the sun's ecliptic longitude on the birth dateSource: Tropical zodiac sign date ranges as used in Western astrology.
Worked example
A birth date of 21 October.
- Libra runs approximately 23 September to 22 October.
- 21 October falls inside that range.
- Element: air. Modality: cardinal.
- It is within two days of the Scorpio boundary, so the year matters.
Libra — an air sign of cardinal modality, close enough to the cusp that the exact year should be checked.
Frequently asked questions
Why do sign dates differ between sources?+
Boundary dates drift by about a day across the leap-year cycle, so sources round differently.
What is a cusp?+
A birthday within a day or two of a boundary. There is no blended sign — the exact moment decides.
What is the difference between sun, moon and rising?+
Sun follows the date, moon changes every two to three days, and rising depends on birth time and location.
Why does Vedic astrology give a different sign?+
It uses the sidereal zodiac, which accounts for precession and shifts signs by roughly 24 degrees.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.