Matsya Purana — Measures of Time: Caturyuga Computation
अष्टौ शतसहस्राणि वर्षाणां मानुषाणि तु चतुःषष्टिसहस्राणि वर्षाणां द्वापरं युगम् //
aṣṭau śatasahasrāṇi varṣāṇāṃ mānuṣāṇi tu catuḥṣaṣṭisahasrāṇi varṣāṇāṃ dvāparaṃ yugam //
The Dvāpara Yuga consists of 800,000 human years, with an additional 64,000 years.
It does not describe Pralaya directly; it gives a technical yuga-duration used to situate creation, decline of dharma, and periodic dissolutions within a larger cosmic timetable.
By defining Dvāpara’s timescale, it frames the Matsya Purana’s ethical idea that dharma and social duties vary by yuga; rulers and householders are to follow yuga-appropriate conduct as righteousness wanes across epochs.
No direct Vāstu or ritual rule appears here; however, yuga-calculations are often used in Purāṇas to contextualize when particular temple-building traditions, rites, and dharma-practices are said to flourish or decline.