Amāvasyā-Pitṛtarpaṇa: Purūravas and the Soma-Based Ancestral Offering (अमावस्या-पितृतर्पण / सोमतर्पण-विधि)
प्रतिपत्कृष्णपक्षस्य काले ऽतीते ऽपराह्णके / सायाह्ने प्रतिपन्ने च स कालः पौर्णमासिकः
pratipatkṛṣṇapakṣasya kāle 'tīte 'parāhṇake / sāyāhne pratipanne ca sa kālaḥ paurṇamāsikaḥ
On the pratipadā of the dark fortnight, when the aparāhṇa has passed and evening has set in, that very time is called the paurṇamāsika time.