Manasara 30.92

30.92

śeṣaṃ tadvāremityuktaṃ arkavārādivārayuk
tribhirvedāstu vṛddhiḥ syānnandahāni navāṃśakam

The remainder is declared to be the weekday, possessing the weekdays beginning with Sunday; / With [multiplication by] three or four there is an increase, and a deduction by nine gives the nine fractional portions;