Vijaya Ekadashi occurs during the waning phase of moon (Krishna Paksha) in February – March. In 2015, the date of Vijaya Ekadashi is February 15. The greatness of this Ekadasi is mentioned in the Skanda Purana and observing of Vijaya Ekadasi helps in removing all the guilt associated with sins committed and also helps in attaining victory. It is believed that Lord Ram observed Vijaya Ekadashi to cross the ocean to reach Lanka and defeat Ravana.
The importance of Vijaya Ekadasi was narrated to Narada by Lord Brahma. Legend has it that when Lord Ram and his army – the Vanarasena – was searching for a means to cross the ocean to reach Lanka, Lakshmana mentioned about a great a Sage who lived nearby and said that perhaps he might provide us with a solution.
It is this sage who mentioned about Vijaya Ekadashi to Lord Ram and its benefits – observing it will help in being victorious.
All the normal rules associated with Ekadashi fasting is observed during Vijaya Ekadasi. Some people don’t sleep on the day. Grains and food made of rice are strictly avoided.
source – http://www.hindu-blog.com/2009/02/vijaya-ekadashi.html