Magha Shukla Ashtami is death anniversary of Bhishma Pitamah, one of the most prominent characters of the great Indian epic, the Mahabharata and this day is known as Bhishma Ashtmai. Bhishma bowed for celibacy and followed it throughout his life. Due to his loyalty and devotion to his father Pitamah Bhishma was blessed with boon to choose the time of his death.
When he got injured in the battle of Mahabharata he didn’t leave his body due to his boon. He waited for the auspicious moment to give up his body. According to Hindu belief God Suryadev moves in South direction during half of year which is inauspicious period and all auspicious activities are postponed till Suryadev starts moving back in North direction. Pitamah Bhishma chose Magha Shukla Ashtami to give up his body and by this time Suryadev started moving back in North direction or Uttarayana (उत्तरायण).
This day People do Ekodishta (एकोदिष्ट) Shradhha for him. His Shradhha has been prescribed for those who have lost their father. However many believe that his Shradhha rituals can be performed by all irrespective of their father being alive or dead.