Narada Purana — Purva Bhaga, Shloka 53
Tithi-Nirṇaya for Vratas: Ekādaśī Rules, Saṅkrānti Punya-kāla, Eclipse Observances, and Prāyaścitta
एकादशी यदाविद्धा द्वादश्यां न प्रतीयते । द्वादशी च त्रयोदश्यामस्ति तत्रैव चापरे ॥ ५३ ॥
ekādaśī yadāviddhā dvādaśyāṃ na pratīyate | dvādaśī ca trayodaśyāmasti tatraiva cāpare || 53 ||
当十一日（Ekādaśī）的月日被“穿入/重叠”（相互交叠）而不被认定为落在十二日（Dvādaśī）之中，又当十二日（Dvādaśī）本身延续至十三日（Trayodaśī）时——就在这种情形下，有些权威传承另立不同的守戒法。
Sanatkumara (teaching Narada in the Ekadashi-vrata context)
Vrata: Ekadashi
Primary Rasa: shanta
Secondary Rasa: none
FAQs
It emphasizes that devotional vows like Ekādaśī are not merely emotional acts but must be performed with correct tithi discernment; accuracy in observance protects the sanctity and intended merit of the vrata.
Bhakti here is expressed through disciplined Vishnu-oriented vrata practice—showing that devotion includes careful adherence to sacred time (kāla) and scriptural procedure when tithis overlap.
Vedāṅga Jyotiṣa (calendar/astronomical timekeeping) is implied—specifically the rule-based evaluation of tithi ‘viddha’ (overlap) and how that affects Ekādaśī fasting and Dvādaśī-related decisions.