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

CHAPTER XI
Brahmagupta’s
Astronomy : Its Highlights
Beginning or Starting Point
Very often in Indian astronomy, we come across a term
ahargaṇa (literally meaning collection of days), which means
the number of mean civil days elapsed at mean Sunrise at Laṅkā
on a given lunar day (tithi), since the beginning of Kaliyuga. It
is the beginning of Kaliyuga, which is taken as the starting point
for the reckoning of ahargaṇa. This happened on Friday, Febru-
ary 18, B.C. 3102, at mean sunrise at Laṅkā, when the Sun, Moon,
and the planets are supposed to have been in conjunction at the
first point of the nakṣatra Aśvinī (which is a fixed point situated
near the star ζ-Piscium). According to Āryabhaṭa and Bhāskara
I, the duration of Kaliyuga is 1,080,000 solar years. Four times
this (4,320,000) is the duration in solar years of a bigger unit
called Mahāyuga or even yuga.
Laṅkā in Indian astronomy is a hypothetical place where
the meridian of Ujjain (latitude 23° 11′ N, longitude 75° 52′ E
from Greenwich) intersects the equator. It is one of the four
hypothetical cities on the equator called Laṅkā, Romaka,
Siddhapur and Yamakoṭi (or Yavakoṭi). The Sūrya-siddhānta
describes Laṅkā as a great city (mahāpurī) situated on an island
to the south of Bhāratavarṣa.¹ The present Ceylon is not the

1. समन्तान्मेरुमध्यात्तु तुल्यभागेषु तोयधेः ।
   द्वीपेषु दिक्षु पूर्वादिन्नगर्यो देवनिर्मिताः ।।
   भूवृत्त पादे पूर्वस्यां यवकोटीति विश्रु ता ।
   भद्राश्व वर्षे नगरी स्वर्णप्राकारतोरणा ।
   याम्यायां भारतेवर्षे लङ्का तद्वन्महापुरी ।।
   (Cont. on page 290)