What is my rāśi, and why is it different from my sun sign?

in India your rāśi is the sign of the Moon at birth; the “sun sign” in magazines is the Sun's sign in the Western zodiac.

In Vedic astrology, when someone asks “what is your rāśi?”, they mean your Moon sign (candra rāśi) — the sign the Moon occupied when you were born. The Moon moves quickly, about one sign in two and a quarter days, and it is taken as the mirror of the mind, so daily and monthly predictions in Indian pañcāṅgas are read from it.

Western newspaper horoscopes use your sun sign, which depends only on your birth date. On top of that, the Western zodiac is tropical while the Indian one is sidereal, so even the Sun is usually placed about one sign earlier in a Vedic chart. A Western “Leo” is very often a Vedic Cancer Sun.

Neither is “wrong” — they are different systems. For Indian festivals, matching and transits, use the Moon rāśi from a sidereal chart.

Source: Bṛhat Parāśara Horā Śāstra; modern practice · Moon changes sign about every 2¼ days

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