सूर्यरथनिर्णयः (चन्द्रस्य पक्षवृद्धिक्षयविधानम्)
यावत्तु क्षीयते तस्य भागः पञ्चदशस्तु सः अमावास्यां ततस्तस्या अन्तरा पूर्यते पुनः
yāvattu kṣīyate tasya bhāgaḥ pañcadaśastu saḥ amāvāsyāṃ tatastasyā antarā pūryate punaḥ
അതിന്റേത് ക്ഷയിക്കുന്ന അംശം പഞ്ചദശാംശമായി കണക്കാക്കപ്പെടുന്നു; അമാവാസ്യയിൽ അത് അതനുസരിച്ച് കുറഞ്ഞുപോകുന്നു, പിന്നെ ഇടക്കാലത്ത് വീണ്ടും നിറഞ്ഞുവരുന്നു।
Suta Goswami
It links Shiva-puja to sacred time (kāla) by describing the Moon’s waning and waxing that define tithis; observing amāvāsyā and the lunar cycle helps time vrata, abhiṣeka, and dāna in a ritually precise way.
By emphasizing cyclical decrease and replenishment, it points to kāla as a regulated power within creation—while Shiva as Pati is the transcendent lord of kāla, the Pashu experiences change and rhythm through such cosmic measures.
Tithi-based observance—especially amāvāsyā-related rites (vrata, śrāddha, japa, and Shiva-abhiṣeka)—supporting Pashupata discipline through regularity and mastery over time-bound impulses (pāśa).