Matsya Purana — Solar–Lunar Motions
त्रिंशत्कलो मुहूर्तस्तु अहस्ते दश पञ्च च ह्रासो वृद्धिरहर्भागैर् दिवसानां यथा तु वै //
triṃśatkalo muhūrtastu ahaste daśa pañca ca hrāso vṛddhiraharbhāgair divasānāṃ yathā tu vai //
Thirty kalās make one muhūrta, and a day consists of fifteen muhūrtas. The shortening and lengthening of the days occur in accordance with the portions (lengths) of daylight, as is indeed taught.
This verse is not about Pralaya; it defines units of time (kalā, muhūrta) and explains how day-length increases or decreases—knowledge used to compute seasons and ritual timing rather than cosmic dissolution.
By defining muhūrtas and the changing length of days, it supports correct scheduling of daily disciplines—royal administration, household rites, fasting days, and seasonal observances—so actions are performed at proper times.
Muhūrta-knowledge is foundational for choosing auspicious times for rituals, consecrations, and building activities; the verse provides the underlying time-units used in selecting proper muhūrtas.