Matsya Purana — Measures of Time: Caturyuga Computation
त्रिंशद्ये मानुषा मासाः पित्र्यो मासः स उच्यते शतानि त्रीणि मासानां षष्ट्या चाभ्यधिकानि तु पित्र्यः संवत्सरो ह्येष मानुषेण विभाव्यते //
triṃśadye mānuṣā māsāḥ pitryo māsaḥ sa ucyate śatāni trīṇi māsānāṃ ṣaṣṭyā cābhyadhikāni tu pitryaḥ saṃvatsaro hyeṣa mānuṣeṇa vibhāvyate //
Thirty human months are said to make one month of the Pitṛs. And three hundred and sixty human months—by human reckoning—are indeed regarded as one year of the Pitṛs.
This verse does not describe Pralaya directly; it teaches a cosmological time-conversion showing that time flows differently for the Pitṛs than for humans.
By defining Pitṛ-time, it supports correct timing and understanding of ancestral rites (Śrāddha). A householder—and a king as guardian of dharma—should ensure such rites follow proper calendrical principles.
Its significance is ritual rather than architectural: it provides the doctrinal basis for calculating Pitṛ-related observances by distinguishing human time from Pitṛ-loka time.