Matsya Purana — Solar–Lunar Motions
उत्तरक्रमणे ऽर्कस्य दिवा मन्दगतिः स्मृता तस्यैव तु पुनर्नक्तं शीघ्रा सूर्यस्य वै गतिः //
uttarakramaṇe 'rkasya divā mandagatiḥ smṛtā tasyaiva tu punarnaktaṃ śīghrā sūryasya vai gatiḥ //
When the Sun proceeds on its northward course (uttarāyaṇa), its movement by day is said to be slow; but that very Sun’s motion at night is indeed swift.
This verse does not describe Pralaya directly; it belongs to the Matsya Purana’s cosmological/astronomical instruction, explaining how the Sun’s perceived course differs by day and night during the northward passage.
By grounding time-reckoning in celestial observation, it supports correct scheduling of daily duties and public rites—useful for householders’ nitya-karma timing and for kings overseeing calendrical order, festivals, and ritual observances aligned with uttarāyaṇa.
Ritually, uttarāyaṇa is a key seasonal marker used to time yajñas, dāna, vrata, and other observances; architecturally, such solar knowledge informs temple orientation and calendrical festival planning, though no direct Vāstu rule is stated in this verse.