Jaya Ekadasi is observed on Magh Shukla Ekadashi day, the eleventh day during Shukla Paksha in Magh month. In 2018, Jaya Ekadashi date is January 27 | January 28.
Since Ekadashi tithi begins on 27 January, Smarta Ekadashi is observed on this day. And Ekadashi tithi ends after the sunrise on 28th, Vaishnava Ekadashi is observed on 28th January.
While Magh month is the auspicious month for Shiva puja and this Ekadasi is auspicious for Vishnu Puja. On this day, Lord Vishnu and Shiva both are worshipped. Observing Jaya Ekadasi Vrat gives the devotees the opportunity to get rid of the sins and to get salvation.
The legend or story or Jaya Ekadasi Vrat katha is mentioned in the Padma Purana. It is explained as a conversation between Lord Krishna and Yudhistira. Jaya Ekadasi is known as Bhishma Ekadashi or Bhauma Ekadasi in South India.