The sidereal zodiac is an imaginary belt of 360 degrees, divided into 12 equal parts. Each twelfth part is called a sign or rāśi in Sanskrit. Jyotish and Western zodiacs differ in the method of measurement. While synchronically, the two systems are identical, Jyotish uses primarily the sidereal zodiac in which stars are considered to be the fixed background against which the motion of the planets is measured, whereas most Western astrology uses the tropical zodiac, the motion of the planets is measured against the position of the Sun on the Spring equinox.

This difference becomes noticeable over time. After two millennia, as a result of the precession of the equinoxes, the origin of the ecliptic longitude has shifted by about 22 degrees.

As a result the placement of planets in the Jyotish system is consistent with the actual zodiac, while in western astrology the planets fall into the following sign, as compared to their placement in the sidereal zodiac, about two thirds of the time.