Matsya Purana — Measures of Time: Caturyuga Computation
षट्त्रिंशत्तु सहस्राणि वर्षाणां मानुषाणि च षष्टिश्चैव सहस्राणि संख्यातानि तु संख्यया दिव्यं वर्षसहस्रं तु प्राहुः संख्याविदो जनाः //
ṣaṭtriṃśattu sahasrāṇi varṣāṇāṃ mānuṣāṇi ca ṣaṣṭiścaiva sahasrāṇi saṃkhyātāni tu saṃkhyayā divyaṃ varṣasahasraṃ tu prāhuḥ saṃkhyāvido janāḥ //
Thirty-six thousand human years—and additionally sixty thousand more—are reckoned by calculation; those skilled in enumeration declare that this amounts to one thousand divine years.
It does not describe Pralaya directly; it establishes a technical conversion between human-year counts and “divine years,” a framework used elsewhere to narrate vast cosmic cycles that include creation and dissolution.
Indirectly: by teaching standardized time-reckoning, it supports dharma in practice—ritual calendars, vows, and royal/household observances depend on correct computation of sacred time scales.
No Vāstu rule is stated, but the time-calculation is relevant to ritual timing (muhūrta, calendrical reckoning) that often accompanies temple consecrations and major rites referenced across the Matsya Purana.