Precession
Glossary · Last updated: 2026-07-26
Axial precession is a slow wobble of Earth's rotation axis. It moves the equinox points westward along the ecliptic about one degree every 72 years.
That drift is why tropical Aries no longer sits in front of the constellation Aries. It is also why ayanamsa grows over centuries.
Example: see it on a birth date
Precession is the slow drift that separates tropical and sidereal zodiacs. On April 3, 2021 the tropical sun sign is Aries and the sidereal Moon estimate is Dhanu rashi.
That drift is why the same birthday can get different sign labels in Western and Indian Vedic lists.
Enter your own date on the Zodiac Sign Calculator.
Not your personal shift
Precession does not change your tropical sun sign. It explains why Western and Indian Vedic frames drifted apart over history.
Related
Main reading and tools
These are the main reading and calculator pages. Use them for a daily note, a birth-sign tool, or a pair check.
- Today's Horoscope hubAll twelve Western sun-sign daily pages, plus links to the seven-tradition reader.
- Horoscope & Zodiac CompatibilityTwo birth dates for Western, Chinese, and Indian Vedic pairing, plus every sun-sign hub.
- Zodiac Sign CalculatorWestern sun sign from birth date, with element, modality, and ruler.
- Rising Sign CalculatorIndian Vedic Lagna estimate when you have birth date, time, and place.
- Moon Sign CalculatorIndian Vedic Janma Rashi and nakshatra when birth time and city are available.