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

UNITS OF TIME 295 māsa) in a kalpa (57,753,300,000-4,320,000,000=53,433,300,000 lunar months). By subtracting the number of solar months from the number of lunar months in a kalpa, one gets the number of adhi-māsas (additional-months) : 53,433,300,000-51,840,000,000= 1,593,300,000 adhimāsas. This multiplied by 30 gives the number of lunar days (śaśi-divasa) in a kalpa ; 53,433,300,000×30= 1,602,999,000,000 lunar days. The difference between the lunar days and kudinas in a kalpa gives the number of avama-dinas in a kalpa : 1,602,999,000,000-45,720,000,000=1,556,279,000,000.¹ Brahmagupta calculates out the sṛṣṭi-saṁvatsara or the Creation Era during his year of composition of the Treatise. He says : Six manus have gone in the kalpa ; the seventh manu is now running of which have lapsed 27 caturyugis ; of the twenty eighth caturyugī, the three yugas, kṛta, dvāpara and tretā have gone by and also of the present kaliyuga 3179 years have lapsed. The total period thus lapsed on calculation comes to be 1,972,947,179 years :² Total Period=6 manus+7 manu-sandhis+27 yugas +kṛta+dvāpara+tretā+3179 years of kali. =(6×71×4,320,000 years) +(7×4×432,000 years)+ (27×4,320,000 years)+(1,728,000+1,296,000+864,000)+ 3,179=1,972,947,179 years. =1,840,320,000+12,096,000+116,640,000+3,888,000+ 3,179=1,972,947,179 years. Calculation of Ahargaṇa : The method of calculating ahar- gaṇa (number of days elapsed since the beginning of kaliyuga)

1. परिवर्त्ताः स्वचतुष्टयशराश्वि रसगुणयमद्विवसुतिथयः । रवि भगणोना भानोः सावनदिवसाः कुदिवसास्ते ॥ रवि भगणाख्यब्दा द्वादशगुणिता भवन्ति रविमासाः । भगणान्तरं रवीन्द्वोः शशिमासाः सूर्यमासोनाः ॥ अधिमासाः शशिमासास्त्रिंशद्गुणिता भवन्ति शशिदिवसाः । शशिसावनदिवसान्तरमवमानि तिथिः शशांकदिनम् ॥ —BrSpSi. I. 22-24
2. कल्पपरार्द्धं मनवः षट् कस्य गताश्चतुर्युगत्रिघनाः । त्रीणिकृतादीनिकलेर्गोऽङ्गैक गुणाः शकान्तेऽब्दाः ॥ नवनगशशि मुनिकृत नव यमनगनन्देन्दवः शकनृपान्ते । सार्धमतीतमनूनां सन्धिभिराद्यन्तरान्तर्गैः ॥ BrSpSi. I. 26-27