सूर्यरथनिर्णयः (चन्द्रस्य पक्षवृद्धिक्षयविधानम्)
वृद्धिक्षयौ वै पक्षादौ षोडश्यां शशिनः स्मृतौ एवं सूर्यनिमित्तैषा पक्षवृद्धिर्निशाकरे
vṛddhikṣayau vai pakṣādau ṣoḍaśyāṃ śaśinaḥ smṛtau evaṃ sūryanimittaiṣā pakṣavṛddhirniśākare
Waxing and waning are said to occur at the beginning of the fortnight and at the sixteenth tithi in the Moon. Thus, with the Sun as the determining cause, this increase of the fortnight is established in the night-maker, the Moon.
Suta Goswami (narrating to the sages of Naimisharanya)
It grounds Shiva-puja timing in kala (sacred time): understanding waxing/waning tithis helps choose auspicious vrata and abhisheka days, aligning worship with the cosmic order governed through Sun–Moon measures.
By implying that cosmic regulation (kala-niyati) operates through luminaries, it points to Pati (Shiva) as the transcendent Lord of time, while Sun and Moon function as instruments within His ordered manifestation.
Muhurta- and tithi-based observance—planning vrata, japa, and Linga-abhisheka in harmony with paksha progression; for Pashupata-oriented sadhana, this supports disciplined practice through regulated time.