“If one is capable the Bhisma-panchaka vow will be observed for the sake of love of God for the five days from the eleventh day (of the bright lunar fortnight in Kartika) up till the full moon day. The prescriptions for this have been given in the Vrata-Khanda-Kartika Mahatmya of the Padma-purana, in the Skanda Purana and in the Visnu-rahasya.”
After observing the fast of Prabhodhini Ekadasi in the month of Kartik, one should fast for the last five days of Kartik which are called Bhisma Pancaka