Purusottami Ekadasi is associated with the Ekadashi fasting dedicated to Lord Vishnu. The Ekadasi that is observed in the Adhik Masa or Purushottam Month is usually referred as Purusottami Ekadasi. In 2015, Purusottami Ekadasi dates are June 28 and May 12. The term ‘Purusottami Ekadasi’ is more popular in Orissa.
Adhik Masa or Purushottam Mahina is associated with the Hindu Lunar Calendars. When there is such an occurrence instead of the usual 24 ekadasis in a Hindu Lunar Year there will be 26 Ekadasis,
The two extra ekadasis in a lunar year is referred as Purusottami Ekadasi.