Bhishma Ashtami, or Bhismashtami, is observed on the eighth day of the Shukla Paksha (waxing phase of moon) of Magh Month (January – February) as per traditional Hindu calendar. In 2015, the date of Bhisma Ashtami is January 27. The day is dedicated to Bhisma of Mahabharata, popularly known as Bhisma Pitamaha or Ganga Putr Bhism. It is believed that his soul departed on this day.
Bhisma Pitamaha had got a boon from his father, Shantanu, that he will only die when he wishes. After the 18-day war in Mahabharat, it is believed that Bhisma chose the ashtami day on the Shukla Paksha of Magh month to leave his body and merge with the Supreme Soul. This happened during the auspicious Uttarayan period, the daytime of Devas.
A fast is observed by some communities on the day. In
Bengal special pujas are held on the day.