Vishnu Sahasranama Jayanti is the most auspicious day observed on Shukla Paksha Ekadasi in Magh month. Vishnu Sahasranama Jayanti 2013 date is February 21.
On Magh Shukla Panchami, Bhishma Pitamaha revealed this stotram to Pandavas during Kurukshetra War.
Before his last breath, Bhishma prayer to Lord Vishnu with 1000 names which later on became popular as Vishnu Sahasranama Stotram. Hence, the day is popular as Bhishma Ekadashi.
In fact Bhishma Pitamah left his soul and entered and united with the Lord on Bhishmashtami. Bhishma Ekadasi is also known as Jaya Ekadasi or Bhoumi Ekadasi.
In 2012, Vishnusahasranama Jayanti date was February 3.