Learn

Sidereal vs tropical zodiac: why your sign changes

Both zodiacs divide the ecliptic, the Sun's apparent path, into twelve 30° signs. They differ only in where 0° Aries is anchored.

The tropical zodiac (Western astrology) anchors 0° Aries to the March equinox: the moment the Sun crosses the celestial equator northward. The sidereal zodiac (Vedic astrology, Jyotisha) anchors the signs to the fixed stars.

These two frames drift apart by about 1° every 72 years because Earth's axis precesses, a 26,000-year wobble that slides the equinox backward through the constellations. The accumulated gap is the ayanamsa, currently about 24° (Lahiri ayanamsa, the Indian government standard). That is why a tropical Taurus Moon can be a sidereal Aries Moon: same Moon, same sky, two coordinate systems.

Neither is wrong. Both are equal 30° coordinate systems: tropical is anchored to the equinox, while sidereal uses a fixed-star-linked zero point set by an ayanamsa rather than the unequal constellation boundaries. StarScore computes both for every chart, in the birth chart calculator and the kundli, and the nakshatras are always sidereal.