When the Dwadashi Tithi occurs with certain special combinations in Panchang, it is observed as Mahadwadashi. Scriptures such as the Dharma Sindhu, Nirnaya Sindhu, Narada Purana, Bhavishya Purana and Varaha Purana describe various Mahadwadashi Tithis formed through the combination of specific dates and Nakshatras. This article lists different days of Mahadwadashi, including Unmilini Mahadwadashi, Vanjuli Mahadwadashi, Trisparsha Mahadwadashi, Pakshavarddhini Mahadwadashi, Jaya Mahadwadashi, Vijaya Mahadwadashi, Jayanti Mahadwadashi and Papanashini Mahadwadashi.
To attain the divine grace of Lord Vishnu, one should observe the Mahadwadashi and Dwadashi fasts with full devotion and sincerity. The Dwadashi Tithi is highly beloved to Lord Vishnu. Hence, observing the Dwadashi fast is considered one of the most accessible means to receive His blessings. In the Vaishnava tradition, the Dwadashi fast is regarded as equally meritorious as the Ekadashi fast. On the occasion of Dwadashi, special rituals such as worship and Abhisheka of Lord Vishnu with Tulsi leaves are performed in temples with great devotion.