If a Vedic chart tells you something different from the horoscope app you have used for years, neither one is lying to you.
Western astrology uses the tropical zodiac, which is anchored to the seasons — the spring equinox marks the start of Aries every year, regardless of where the constellations have drifted. Vedic astrology uses the sidereal zodiac, anchored to the fixed stars themselves. Over centuries the two have separated by roughly 24 degrees.
That gap is why so many people meet their Rashi and feel briefly disowned. A lifelong Leo becomes a Cancer. Someone who has explained themselves as a Sagittarius since school reads Scorpio instead. Nothing about you changed; the measuring system did.
The more useful question is what each system is built to do. Tropical placements describe seasonal archetypes and are excellent for psychological framing. Sidereal placements are the base for the Vedic timing tools — Dasha periods, transits over the Moon, the divisional charts — which is where the tradition does its most specific work.
In practice, we read your Rashi as the ground floor and your Moon sign as the room you actually live in. If you want to keep your Sun sign as a piece of personal language, keep it. It costs nothing, and it is not competing with the chart we are reading.
Does every placement move back one sign?
Not always. The two zodiacs are about 24 degrees apart, and a sign is 30 degrees wide. A planet in the last few degrees of a tropical sign stays in the same sign in the sidereal chart; anything earlier moves back one. That is why some people find their Vedic chart familiar and others barely recognise it.
You can see your own sidereal placements with the free birth chart calculator, which runs in your browser. To have them read as one chart rather than one sign at a time, The Self Discovery is the full birth chart reading.