Many people who look up their Vedic rashi find it is not the star sign they have always known. There are two separate reasons, and either one alone is usually enough to change the answer.
Reason one: two different zodiacs
Western astrology uses the tropical zodiac, which starts 0° Aries at the spring equinox. Jyotisha uses the sidereal zodiac, which is anchored to the fixed stars. The two coincided around the early centuries CE, but the equinox slides slowly backwards against the stars — precession, about 50 arcseconds a year, or one degree every 72 years — and they have been drifting apart ever since.
The gap between them is the ayanamsa. This site uses the Lahiri (Chitrapaksha) ayanamsa, which places the star Spica (Chitra) at 0° Libra. It was adopted by the Government of India on the recommendation of the Calendar Reform Committee in 1955, and it is the basis of most published panchangs. In late 2026 it is a little over 24°13′.
So every position in a Vedic chart sits about 24° earlier than in a Western one. Since a sign is 30° wide, anyone whose Sun falls in the first 24° or so of a tropical sign has a sidereal Sun in the sign before — roughly four people in five. A Western Aries born in early April is usually a Vedic Pisces Sun.
Reason two: the Moon, not the Sun
In the West, “your sign” means your Sun sign. In jyotisha, the sign that matters most for daily horoscopes, matching and naming is the Moon sign — the rashi the Moon occupied at birth, also called the janma rashi or Chandra rashi.
The Sun stays in a sign for a month, but the Moon moves through one in about two and a quarter days. Your Moon sign can be any of the twelve, regardless of your Sun sign, and your birth date alone may not settle it. That is why the site asks for your time and place of birth to find your rashi.
How the daily horoscope uses it
A Vedic daily horoscope is read from Chandra gochara — the house the Moon is transiting today, counted from your natal Moon sign. The classical texts hold the Moon’s transit through the 1st, 3rd, 6th, 7th, 10th and 11th houses from the natal Moon as favourable. Because the Moon changes sign every two days or so, the reading changes with it. The per-sign horoscope pages show the full gochara table for each rashi.
Other ayanamshas exist — Raman, Krishnamurti and others differ from Lahiri by up to about a degree and a half. Near a sign boundary, the choice can change the result.