In Hindu religion, Sphuta is the longitude of a moving heavenly body, measured from the fixed point marked by Revati Nakshatra (Zeta Piscium). In the ecliptic system, the position of a body is given by sphuta. If it is found that the number of civil days, called ahargana, had elapsed from the commencement of an epoch up to any point of time, then the mean longitude of any planet can be obtained by dividing the elapsed days by the time period of the planet.
The quotient thus obtained will denote the number of complete revolutions the planet would have performed, and the remainder, expressed in degrees, yields the mean longitude.
Surya Siddhanta introduces the cyclic time of mahayuga, a period of 4,320,000 years, to calculate ahargana, and uses it for finding the mean motion of the planets also. Once the means positions are known, the true position can be obtained from the mean position by making some corrections to them.
The details of such calculations are given in almost all the astronomical texts.
Aryabhata I (b. 476 CE) states that the true motion of the planets is given by the epicycle. The center of the epicycle lies on the normal circular orbit of a planet, giving it mean position. A planet when faster than its ucca (apex of slow or fast motion) moves clockwise on the circumference of its epicycle (manda), and when slower than its ucca moves anticlockwise on its epicycles (sighra). After calculating the mean position of a planet, appropriate corrections (called mandaphala and sighraphala) are applied to get its true position.