Wondering why I am saying this. Well! Since my g'ma left us on this auspicious day and she like Bheeshma Pithamaha was waiting for such an occasion to pass away, I have been asking around on why this is such a great time.
This is auspicious for two pronged reasons.
1. Shree Vishnu Sahasranama (Lord Vishnu's 1000 names) was brought to light on this day :-
When Krishna did the Geethopadesha, Arjuna could understand it only partly and hence did not treat Krishna as the Guru he was. Disappointed Krishna appointed Bheeshma as the Guru to teach the Pandavas (who were the only ones alive by then) the true meaning of Dharma. Bheeshma in turn taught them the Vishnu Sahasranama which is the embodiment of the Geetha and all the Vedas.
2. Bheeshma died shortly after.
When Devavrata took the oath to never marry or rule the kingdom, the devas and celestial beings were impressed with the young man's courage and devotion and bestowed upon him many great boons and rewards. One such boon was that Devavrata (now renamed Bheeshma) could choose the day he wanted to die. Bheeshma chose to die shortly after explaining the Sahasranama and the Ultimate truth of Dharma to Pandavas.