The Sun Treatise

...and brought it to its present form, for which help must have been taken from the works or observations of Aryabhata, Brahmagupta, etc., as Mr. Sengupta Prabodh Chandra Sengupta, a 20th-century historian of Indian astronomy proves in his introduction to the Khandakhadyaka A significant astronomical treatise by Brahmagupta, 7th century CE.

Opinions of Western Scholars —

Regarding its period of composition, Western scholars have engaged in a great deal of deliberation, for which it is our supreme duty to thank them. Mr. Bentley John Bentley (1750–1824), an English scholar who applied mathematical analysis to date Indian texts has put in a lot of effort on this subject. He calculated the positions of the Sun, Moon, and other planets according to the Surya Siddhanta and modern observations for various eras. He then fixed the composition period of the Surya Siddhanta as the specific time when the planetary longitudes original: "bhogansh"; the angular position of a planet along the ecliptic from both calculations coincided. This will be clear from the table on page 14, in which the errors of the planets were shown.

From this, Bentley concludes that the Surya Siddhanta was written in the last quarter of the 11th century. On the surface, this seems very logical, and there is no doubt that the author has shown great innovation in this approach. However, in reality, this method is not worthy of acceptance without thorough examination. I find it sufficient to state this in the words of the Publication Committee for Burgess’s translation referring to the 1860 translation of the Surya Siddhanta by Rev. Ebenezer Burgess:—

“The times Bentley calculated for zero error regarding other planets are very similar to the times we calculated by working backward from the errors of 1860 CE, which are given with the commentary on the 67th verse.”

“Upon comparing these two tables, it will immediately be seen that Bentley did not derive his decision from the errors in the absolute positions of the planets, but rather in comparison to the position of the Sun. However, he did not even consider the error in the Sun's position. The Hindus' zodiac is Sidereal original: "Nakshatrika"; a system of tracking planets against the fixed stars rather than the seasons and is in no way dependent on the movement of the Sun. Like other planets, the Sun was also not at that position in 3102 BCE The traditional start of the Kali Yuga where it was assumed to be, and therefore the speed of the Sun assumed according to this method differs from reality because the sidereal year was assumed to be 3.5 minutes longer than it actually is. Therefore, why should the error of the Sun not be considered, and why should the sidereal motion of the planets be considered only in comparison to this erroneous motion? It is evident that Bentley should have also fully considered the Sun's position and shown whether the same result follows from it as from the calculation of other planets; and if not, what was the reason for the inconsistency? Such...”