ब्राह्मस्फुटसिद्धान्त (ब्रह्मगुप्त - शून्य, कुट्टक, बीजगणित एवं सम्पूर्ण २१ अध्याय सान्वय सटीक)

60 BRAHMASPHUṬA SIDDHĀNTA & KHAṆḌAKHĀDYAKA treatise (i.e. Khaṇḍakhādyaka, literally meaning food prepared from sugar-candy) is made so as to yield the same results as that.¹ The mean saturn diminished by 3 seconds, the Śīghrocca of Mercury diminished by 22 seconds, the mean Mars increased by 2 seconds and the mean Jupiter increased by 4 seconds are equal to the respective mean planets of Āryabhaṭa's midnight system.² In the Brāhmasphuṭasiddhānta, Brahmagupta accepts the astronomical day to begin with the sunrise at Laṅkā, and the calculations of days, months, years, Yugas, and Kalpas all begin from Caitra Śukla Pratipadā (the first tithi of the month Caitra in the bright-half of the Moon) and the first day is regarded as Sunday.³ Varāhamihira in his epicyclic cast to the Sūryasiddhānta in his Pañcasiddhāntikā adopts the ardharātrika system or the system of reckoning days from midnight. The question why Brahmagupta who was so bitter an opponent of Āryabhaṭa I in his younger days (628 A.D.) claimbed down to describe and teach one of the systems of Āryabhaṭa's astronomy in his sixty- seventh year (665 A.D.) is difficult to explain. In fact so great was Āryabhaṭa's reputation and fame that in spite of Brahma- gupta's severe ricticisms of the former in Chapter XI of the Brāhmasphuṭasiddhānta, it perhaps was undiminished and it was Āryabhaṭa who continued to be universally followed. Some authorities have thus expressed the view that to meet the popular demand Brahmagupta in the Khaṇḍakhādyaka took upon himself the task of simplifying Āryabhaṭa's ardharātrika system and in this task he became eminently successful. But it has been supposed that in this task he could not be a mere simplifier or expounder. प्रायेणार्यभटेन व्यवहारः प्रतिदिनं यतोऽशक्यः । उद्वाहजातकादिषु तत्समफल लघूक्तरोक्ति रतः ॥ तिसृभिः शनिज्ञैशीघ्रं द्वाविंशत्या कुजोऽधिको द्वाभ्याम् । चतसृभिरधिको जीवोऽर्द्धरात्रिकार्य्यभट मध्य समाः ॥ —KK. I. 1,2,7 ☛ चैत्रसितादेरुदयाद्भानोर्दिनमासवर्षयुगकल्पाः । सृष्ट्यादौ लंकायां समं प्रवृत्तः दिनेऽर्कस्य ॥ —BrSpSi I.4