Ayanamsha

The Earth's axis wobbles slowly over a 25,772-year cycle. This wobble (precession) means the sky's actual star positions drift relative to the seasonal tropical zodiac at roughly 50 arc-seconds per year. Vedic astrology uses the sidereal zodiac, which is anchored to the actual stars, so it must subtract an offset — the ayanamsha — from any tropical longitude to get the sidereal one. The current ayanamsha is around 24 degrees. Different schools use slightly different values: Lahiri (the Indian government standard) is the most widely used, but Raman, Krishnamurti and Fagan-Bradley schools each define it differently, which can shift planet positions by up to a degree.