Matsya Purana — Measures of Time: Caturyuga Computation
द्वे सहस्रे द्वापरं तु संध्यांशौ तु चतुःशतम् सहस्रमेकं वर्षाणां कलिरेव प्रकीर्तितः द्वे शते च तथान्ये च संध्यासंध्यांशयोः स्मृते //
dve sahasre dvāparaṃ tu saṃdhyāṃśau tu catuḥśatam sahasramekaṃ varṣāṇāṃ kalireva prakīrtitaḥ dve śate ca tathānye ca saṃdhyāsaṃdhyāṃśayoḥ smṛte //
The Dvāpara Yuga is said to be two thousand (divine) years, with its twilight portions (sandhyā and sandhyāṃśa) totaling four hundred. Kali Yuga is proclaimed to be one thousand years, and for it the twilight and the twilight’s fraction are remembered as two hundred and another two hundred.
It does not describe Pralaya directly; it provides the time-measurements of Dvāpara and Kali Yugas (including their junction periods), which are used in Purāṇic cosmology to situate cycles of creation, maintenance, and dissolution in vast chronological frameworks.
By defining the yuga context—especially Kali’s shorter span and its junction periods—the text frames why dharma-protection becomes more urgent in later ages; kings and householders are expected to uphold order and ethical conduct with greater vigilance as time declines.
No direct Vāstu or temple rule is stated; however, yuga-measurements are often used to time rituals, calendrical observances, and Purāṇic chronologies that can govern when major consecrations or commemorative rites are ideally performed.