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
Der Anteil, der schwindet, gilt als der fünfzehnte Teil; zur Amāvāsyā (Neumond) ist er entsprechend vermindert, und danach füllt er sich in der Zwischenzeit wieder (nimmt erneut zu).
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).