Nilamatapurana 751

751

tataḥ pañcadaśīṃ prāpya kṛṣṇāṃ pitryarkṣasaṃyutām
pitṝṇāṃ tarpaṇaṃ kāryaṃ śrāddhaṃ kāryaṃ prayatnataḥ

Then, when the dark fifteenth day conjoined with the constellation belonging to the ancestors has arrived, / water libations to the ancestors should be made, and an ancestral rite carefully performed.