Different systems put a different planet first
Ask someone in London or Chicago what sign they are and you get a Sun sign — the sign the Sun occupied on their birthday. Ask the same question in India and the usual answer is a rashi, which is the sign the Moon occupied at the moment of birth. Neither tradition ignores the other body. Western charts include the Moon; Vedic charts include the Sun, called Surya, and read it for vitality, authority and the father. The difference is one of billing. Western practice made the Sun the headline because it can be worked out from a date alone, while Vedic practice built its whole predictive machinery around the Moon, so the Moon sign became the shorthand people quote.
What a rashi actually is
Rashi simply means sign — one of the twelve 30° divisions of the zodiac, with names that translate straight across: Mesha is Aries, Vrishabha is Taurus, Karka is Cancer, and so on down the list. When someone says "my rashi is Vrishchika" they mean their Moon was in Scorpio when they were born. Because the Moon crosses a sign in about two and a quarter days, a rashi cannot be read off a birthday the way a Sun sign can; two people born a week apart in the same year usually have different ones. That speed is exactly why the Moon carries so much weight in this system: it is the fastest-moving marker in the chart and therefore the most personal.
The lagna, and why your birth time matters
The second thing a Vedic astrologer asks for is the lagna, or ascendant — the sign that was climbing over the eastern horizon at the exact moment and place of birth. Because Earth turns once a day, the whole zodiac passes the horizon every twenty-four hours, and the rising sign changes roughly every two hours. Miss the time by a couple of hours and you have the wrong lagna, which reshuffles the entire house structure of the chart. This is why a Vedic reading asks for a clock time and a birthplace while a magazine horoscope asks for nothing but a date. A date alone can produce a Sun sign; it cannot produce a chart.
Why "what is my Vedic sun sign" misses the point
The question has an answer, and the answer is usually not the sign you know. Because the sidereal zodiac sits about 24.2° behind the tropical one, every Western sign range straddles a single sidereal boundary, with the earlier and larger part of it falling into the previous sign. A Western Leo, born between 22 July and 22 August, is a Vedic Cancer up to about 16 August and a Vedic Leo after that — and the boundary wobbles by about a day with the leap-year cycle, so it is worth calculating rather than assuming. But converting your Sun sign and stopping there imports a Western habit into a system that does not share it. The Vedic answer to "what sign am I" is the rashi and the lagna.
Holding both without contradiction
People often expect to have to pick one and discard the other, and feel some loyalty to the sign they grew up with. There is no need. The two systems are describing the same birth moment with different coordinate origins and different priorities, rather than competing to describe the same thing. A useful way to hold it: your Western Sun sign is a statement about where the Sun stood relative to the season, and your rashi is a statement about where the Moon stood relative to the stars. Both are true readings of the same sky. If you want to explore the Vedic side, start by calculating your Moon sign and lagna properly — that is the doorway, not a translated Sun sign.