Matsya Purana — Sādhāraṇa Śrāddha: General Ancestral Rite
फाल्गुनस्य ह्य् अमावास्या पौषस्यैकादशी तथा आषाढस्यापि दशमी माघमासस्य सप्तमी //
phālgunasya hy amāvāsyā pauṣasyaikādaśī tathā āṣāḍhasyāpi daśamī māghamāsasya saptamī //
The new-moon day of Phālguna, the eleventh lunar day of Pauṣa, the tenth lunar day of Āṣāḍha, and the seventh lunar day of the month of Māgha are to be observed with special regard.
This verse does not discuss Pralaya; it focuses on calendrical discipline—highlighting specific lunar days in particular months as important for observance.
It supports dharmic governance and household life by prescribing recognized sacred dates (tithis) for vows/fasts and ritual restraint, helping maintain social and personal order through regular observances.
The significance is ritual timing: it identifies specific tithis (Amāvāsyā, Ekādaśī, Daśamī, Saptamī) in named months as especially suitable/important for vrata and related rites.