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Introduction

The primary ancient astronomers of the earliest times also considered the state of the AyanamshaThe longitudinal difference between the tropical and sidereal zodiacs, often referred to as the precession of the equinoxes. to be oscillating (moving back and forth). However, it was Vishnuchandra, the author of the Vashistha Siddhanta, who first revealed the revolution of the equinoctial points as a full circle.

According to the view of Aryabhata, in one KalpaA vast cosmic period or "aeon" in Hindu cosmology.—that is, in 4,320,000,000 years—there are 1,582,237,500,000 sidereal risings (rotations of the stars); therefore, in these many years, there are 1,577,917,500,000 days. Many later astronomers have used the measurements of years determined by Aryabhata in their own respective books. The author of the Brahma Siddhanta wrote that in one Kalpa there are "fifteen trillion, eight hundred twenty-two billion, three hundred sixty-four million, five hundred thousand" sidereal risings. Brahmagupta, the author of the Brahma-sphuta-siddhanta, also wrote the same. As follows:—

The planetary calculations spoken by Brahma, which had become corrupted over a great length of time, are now being clearly stated by Brahmagupta, the son of Jishnu. Those whose vision is blocked by the veil of ignorance and who speak differently from the Brahma Siddhanta—I shall explain the errors they make regarding the differences in the start of the Yugas and other matters. In one Kalpa, there are 1,582,236,450,000 sidereal risings.
Original Sanskrit: "ब्रह्मोक्तं ग्रहगणितं... प्रति नक्षत्रोदया ॥"

Because the aforementioned planetary calculations made by Brahma had become obsolete due to being ancient, Brahmagupta, the son of Jishnu, writes a "corrected" version (Sphuta). He describes the faults regarding the differences in the start of the ages (Yugas) found in the words of those ignorant people who deviate from the Brahma Siddhanta. In one Kalpa, there are 1,582,236,450,000 sidereal risings.

Bhaskaracharya, who held Brahmagupta in the highest regard, also published the year measurements and sidereal positions determined by Brahmagupta in his work, the Shiromani.

The author of the Surya Siddhanta and other primary astronomers have conceptualized the AyanaThe movement of the solstice/equinox. as being in an unstable or oscillating state. However, to refute this view, Bhaskara wrote in the Vasana Bhashya: "If this was the case, even if not directly observed, why did the authors of the Surya Siddhanta not describe it as a full circular revolution, similar to the circumference of the planetary orbits, based on the authority of the scriptures?" Original Sanskrit: "यद्येवमनुपलब्धोऽपि... कथं तैर्नोक्तः ।" That is to say, if the era of the Surya Siddhanta and others was entirely consistent regarding the Ayanamsha, why did they not reveal the view of the stellar sphere revolving like a circumference, following the opinion of the man (Vishnuchandra) in the Vashistha Siddhanta? However, Bhaskaracharya expressed this opinion without truly knowing the reason, which shall be written later. It is written in the Surya Siddhanta: