Surya Siddhanta
त्रिम्शत्कृत्यो युगे भानाम् चक्रम् प्राक् परिलम्बते । तद्गुणाद् भूदिनैर् भक्ताद् द्युगणाद् यद् अवाप्यते ॥
The circle of Asterisms librates 600 times in a great Yuga (that is to say, all the Asterisms, at first, move westward 27°. Then returning from that limit they reach their former places. Then from those places they move eastward the same number of degrees; and returning thence come again to their own places. Thus they complete one libration or revolution, as it is called. In this way the number of revolutions in a Yuga is 600 which answers to 600,000 in a Kalpa). Multiplying the Ahargaṇa (or the number of elapsed days) by the said revolutions and dividing by the number of terrestrial days in a Kalpa; the quotient is the elapsed revolutions, signs, degrees, &c.
english translation
trimzatkRtyo yuge bhAnAm cakram prAk parilambate । tadguNAd bhUdinair bhaktAd dyugaNAd yad avApyate ॥
hk transliteration by Sanscript