Matsya Purana — Characteristics of Dvāpara and Kali Yugas
पूर्णे वर्षसहस्रे द्वे परमायुस्तदा नृणाम् निःशेषे द्वापरे तस्मिंस् तस्य संध्या तु पादतः //
pūrṇe varṣasahasre dve paramāyustadā nṛṇām niḥśeṣe dvāpare tasmiṃs tasya saṃdhyā tu pādataḥ //
When two full thousand years have elapsed, that is the maximum lifespan of human beings at that time. And when that Dvāpara Yuga comes to its complete end, its twilight-period (yuga-sandhyā) is only one quarter in measure.
It does not describe Pralaya directly; it gives a chronological rule for yuga-measurement—human lifespan in a given age and the proportional length of the yuga’s twilight (sandhyā) at the end of Dvāpara.
By linking social conditions to yuga-time (shorter lifespans and transitional ‘sandhyā’ phases), it frames why kings and householders must adapt discipline and dharma-practice to declining capacities across ages—prioritizing righteous governance and efficient observance.
No Vāstu or iconographic rule is stated; the ritual takeaway is temporal—rites and dharma are to be understood within yuga divisions and their sandhyā junctions, which are treated as distinct transitional periods in Purāṇic time-reckoning.