Ekadashi or Ekadasi according to Hindu calendar is known as the 11th day or 11th tithi of every lunar month. The meaning of Ekadashi or Ekadasi is eleven (11). It is considered as a spiritually beneficial day to the Hindus and to the Jains. According to Hindu calendar and positions of the moon, a month has 2 ekadashis, therefore a month is divided into two parts of fifteen days (15 days).
Story of King Yudhishthir: The eldest brother of Pandavas in Mahabharata King Yudhishthir, asked the importance of Apara Ekadashi during one of his resting periods. This festival is mainly celebrated among the Hindu communities so that their past sins could wash out easily and people can easily remain in peace. Lord Krishna gave a perfect reply and this was a good example to people in modern days that maintained and observed fast on this Apara Ekadashi and realizes the benefits on an overall.