Matsya Purana — Sādhāraṇa Śrāddha: General Ancestral Rite
अयने विषुवे युग्मे सामान्ये चार्कसंक्रमे अमावास्याष्टकाकृष्णपक्षे पञ्चदशीषु च //
ayane viṣuve yugme sāmānye cārkasaṃkrame amāvāsyāṣṭakākṛṣṇapakṣe pañcadaśīṣu ca //
During the ayana (solstices), the viṣuva (equinoxes), the paired periods (yugma), on common occasions, and also at the Sun’s ingress into a new zodiac sign (ārka-saṅkrama); likewise on amāvāsyā (new-moon day), on the Aṣṭakā days, in the dark fortnight (kṛṣṇa-pakṣa), and on the fifteenth lunar days (pañcadaśī)—these times are to be taken into account for observance.
This verse is not about pralaya; it is a kāla-nirṇaya (time-determination) instruction listing calendrical junctions—solstices, equinoxes, saṅkrānti, Amāvāsyā, Aṣṭakā, and key tithis—considered significant for rites.
It guides kings and householders in choosing ritually potent times for dharma—vratas, donations, and ancestral observances—by prioritizing major solar/lunar transitions (ayana, viṣuva, saṅkrānti) and tithis like Amāvāsyā and the fifteenth day.
The significance is primarily ritual: these are auspicious/ritually weighty time-markers used to schedule observances (especially Aṣṭakā-related śrāddha and Amāvāsyā rites), a common planning principle in Matsya Purana’s dharma sections.