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

292 BRAHMAGUPTA'S ASTRONOMY ITS HIGHLIGHT
sandhyā of 1.296.000/12; i. e. 108.000 years and at the close of
tretā a sandhyāṁśa of 108,000 years. Again, in the beginning
of dvāpara we have a sandhyā of 864.000/12, i. e. 72.000 years
and at the close of dvāpara a sandhyāṁśa of 72000 years; and
similarly at the beginning a sandhyā and at the close a
sandhyāṁśa of 432.000/ 1, i. e. of 36,000 years in the case of kali.
In this respect Brahmagupta appears to follow Manu. the first
author or giver of law. He regards further the following
divisions of time :¹
71 yugas =1 manu
14 manus =1 kalpa
Again, in the beginning, at the middle and at the close of
each manu, there are sandhis, each equal to the measure of kṛta.
Thus, taken as a whole
1 kalpa=71×14 yugas+15 sandhyā-sandhyāṁśa
=994 yugas+15×duration of kṛta
=994 yugas+15×(4×432,000) years
=994 yugas + 6 yugas =1000 yugas
= 1 Brahma-dina (Brahmā's day)
Thus Brahmā's day is regarded as 1 kalpa or one thousand
caturyugis or 1000 yugas or the same as 1000 mahāyugas).
Āryabhaṭa regards a manu to consist of 72 yugas and
therefore a kalpa according to him would be of 14×72 yugas, or
1008 yugas.² Since in the foreign Siddhāntas like Romaka, there
is no reference to yuga, manu and kalpa. Brahmagupta regards
these systems to be unauthoritative.³
We have said that our starting point was the beginning of
Kaliyuga, Friday February 18, B.C. 3102, at mean rise at Laṅkā,
when the Sun, Moon and the planets are supposed to have been
in conjunction at the first point of the Nakṣatra Aśviṇī. This
type of conjunction would again happen after a period of kalpa.

1. मनुरेकसप्ततियुगः कल्पो मनवश्चतुर्दश मनूनाम् ।
   आद्यन्तरान्त सन्धिषु कृतकालोऽस्माद्युग सहस्रम् ॥ —BrSpSi. I. 10
2. दिव्यं वर्ष सहस्रम् ग्रहसामान्यं युगं द्विषट्क गुणम् ।
   अष्टोत्तरसहस्रं ब्राह्मो दिवसो ग्रहयुगानाम् ॥ —Ārya. III. 8
3. युगमन्वन्तरकल्पाः कालपरिच्छेदकाः स्मृतावुक्ताः ।
   यस्मान्नरोमके ते स्मृतिबाह्यो रोमकस्तस्मात् ॥ —BrSpSi. I- 13