Vedic astrology measures planets against the fixed stars (sidereal zodiac); Western astrology measures them from the spring equinox (tropical zodiac). Because of precession the two drift apart by about 1° every 72 years. The gap — the ayanamsa — is about 24° today. India’s standard is the Lahiri (Chitrapaksha) ayanamsa, which anchors the zodiac to the star Spica (Chitra).
What is precession?
Earth’s axis slowly wobbles like a spinning top, completing a circle in about 25,800 years. As a result, the point of the spring equinox moves backwards through the constellations by roughly 50 arc-seconds per year. The tropical zodiac moves with the equinox; the sidereal zodiac stays with the stars.
What is the Lahiri ayanamsa?
In 1955 the Indian government’s Calendar Reform Committee, chaired by Meghnad Saha with N. C. Lahiri as a member, adopted an ayanamsa that places the star Spica (Chitra) at exactly 0° Libra (180°) in the sidereal zodiac. Known as the Lahiri or Chitrapaksha ayanamsa, it is used for the Indian national calendar and by most Indian astrologers. In 2026 it is about 24°13′.
Why does my sign change?
Subtract the ayanamsa from a tropical position to get the sidereal one. A Sun at 10° tropical Aries (around 31 March) becomes about 16° sidereal Pisces. So if you were born in the first three weeks or so of a Western sign, your Vedic Sun sign is likely the previous sign.
| Sidereal sign | Sun’s approximate dates |
|---|---|
| Mesha (Aries) | 14 Apr – 14 May |
| Makara (Capricorn) | 14 Jan – 12 Feb |
| Tula (Libra) | 17 Oct – 15 Nov |
Do Vedic astrologers use the Sun sign?
Mostly they use the Moon sign (rashi) and ascendant. Newspaper rashifal columns in India are usually by Moon sign. Use our free kundli tool to find yours.
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