All the vaishnavas, in accordance with the scriptures, observe with great faith and devotion the tithi of Ekadashi, which is also known as hari vasara, the day of Lord Hari, and Bhakti janani, the mother or the giver of Bhakti. However, there are occasions when the dwadashi tithi, the twelfth day according to the lunar calendar which is also the next day of Ekadashi, becomes a Mahadwadashi, and in that situation, the injunction is that one is supposed to fast on Mahadwadashi instead of Ekadashi. There are eight Mahadwadashi’s which occur due to various calculations of the Tithis and are to be observed by all the devotees with great respect.
Today is the auspicious day of Vyanjuli Mahadwadashi, which occurs when the dwadashi tithi touches two consecutive sunrises. When this happens, the first day is observed as Mahadwadashi, and all the devotees fast on this day instead of the previous day Ekadashi. This year the dwadashi following Utthan Ekadashi in the bright fortnight of Kartik is being observed as Vyanjuli Mahadwadashi. On this auspicious day all the vaishnavas endeavor to increase their chanting and reading and reduce the needs of the body, thus absorbing themselves in the devotional service of the Lord.
This day also marks the beginning of Bhishma Panchaka, the last five days of Kartik, when Bhishma dev fasted for the pleasure of the Lord. The devotees also follow Bhishma panchak in accordance with their capacity. Some follow the strict rules of this fast as given in the shastras, while others may choose to refrain from certain kinds of foodstuffs and increase their chanting and reading during these days. The true purpose of all of these fasts and festivals is to actually increase our remembrance of the Lord and reduce our engrossment in material life. Therefore, regardless of what physical austerities one may decide to do, one should definitely devotee more time in the service of the Lord and in chanting the holy names of the Lord.