Ekadashi is the eleventh tithi of each lunar fortnight. It falls twice a month — once in Shukla Paksha (waxing Moon) and once in Krishna Paksha (waning Moon) — so there are usually 24 Ekadashis a year, and 26 in a year with an Adhika (extra) month. Each one has its own name and story, most of them narrated by Krishna to Yudhishthira in the Padma and Bhavishya Puranas.
Devotees of Vishnu observe a fast from sunrise on Ekadashi until the fast is broken (parana) after sunrise on the following day, Dwadashi. Grains and beans are avoided; many keep a fruit-and-milk fast or, on Nirjala Ekadashi, abstain even from water. The day is spent in prayer, reading the Vishnu Sahasranama or Bhagavad Gita, and night vigil.
Dates on this page follow the Smarta convention: Ekadashi is observed on the day the Ekadashi tithi prevails at sunrise. Vaishnava (ISKCON) calendars sometimes fast a day later when Ekadashi is touched by Dashami before sunrise.