Matsyapurana 141.48

141.48

divā parva tvamāvāsyāṃ kṣīṇendau dhavale tu vai
tasmāddivā tvamāvāsyāṃ gṛhyate yo divākaraḥ //

When the Sun and Moon separate, that period is termed Anvahuti and is known as the time for Vasaṭkriya when the performance of Vasaṭ has been ordained. This period in the Amâvasya is known as Ṛitumukha or the face of the season when Śrâddha should be performed. When the crescent Moon unites with the Sun during the day, that is the time for the abovementioned Parva. The time when the voice of the cuckoo ‘Coo’ ceases, is called “Kuhû.” When the waning Moon of the Amâvâsyâ enters into the Sun, that period is known as Sinîvâlî. The periods Anumati, Râkâ Sinîvalî and Kuhû last for only two lavas. Kuhû lasts as long as “Kuhû” is uttered. The union of all the Parvas lasts for two lavas and both the unions, before and after, are equal. The sacrifices and Vasaṭ rites should be performed as prescribed during those periods. The Vyatipâta yoga of the Sun and the Moon (i.e., their conjunction) and the Pûrṇimâ (their opposition) are productive of the same fruits. The union in the Pratipada tithi lasts for a period of two lavas. Kuhû and Sinîvâlî last for two lavas.—46-53.