Dvādaśī — The Day of Breaking the Sacred Fast
Dvādaśī (the twelfth lunar day, dvā = two, daśa = ten, hence 'twelfth') occupies a position of equal importance to Ekādaśī (the eleventh day) in Śrī Vaiṣṇava observance — for while Ekādaśī is the day of the fast itself, Dvādaśī is the day on which the fast must be correctly broken, and its observance completed. The two days together form a single uninterrupted act of worship.
The act of breaking the fast on Dvādaśī is called pāraṇa ('that which completes/fulfils'). The pāraṇa must occur within a precise window: after sunrise on Dvādaśī but before the Dvādaśī tithi ends. Missing this window — whether by breaking the fast too early (still Ekādaśī) or too late (already Trayodaśī, the thirteenth) — invalidates the Ekādaśī observance. The pāraṇa begins with receiving tulasī-tīrtham (tulasī-steeped water from the Lord's feet), symbolizing that the fast is broken not with ordinary food but with Bhagavān's grace. This is followed by eating a full meal.
Certain Dvādaśī tithis carry special significance. Vaikuṇṭha Dvādaśī (the Dvādaśī of Mārgazhi month, Dhanurmāsa, in the Śukla Pakṣa) follows Vaikuṇṭha Ekādaśī — the most auspicious Ekādaśī in the Śrī Vaiṣṇava calendar when the Vaikuṇṭha Dwāram (the northern gate of Śrī Raṅgam and other divya-deśams) is opened. On Dvādaśī, Bhagavān is seen as having 'awakened' from His rest; devotees who kept vigil through Ekādaśī now joyfully complete the observance by receiving His darśan and partaking of prasādam. The Dvādaśī pāraṇa thus seals the devotee's union with Bhagavān across the two days.