Kurma Jayanthi, or Koorma Jayanti, is observed on the day when Lord Vishnu incarnated as Kurma or Tortoise. Kurma Avatar is the second of the ten incarnations of Lord Vishnu. The purpose of Kurma Avatar was to keep Mount Mandara intact and help in the process of Samudra Manthan or churning of ocean. In 2010, the date of Kurma Jayanti is May 27.
Kurma Jayanti is observed on the Purnima or full moon day in the month of Vaishakha.
Kurma is also identified with Prajapati or Brahma. Prajapati took the form to continue creation. But the popular Kurma incarnation is that of Lord Vishnu.
To fight the Asuras and defeat them for once and all, Devas was advised to churn the ocean and get Amrut (potion of immortality) by Lord Vishnu. To churn the ocean, Devas need the help of Asuras, Mountain Mandara, and Snake Vasuki.
Mountain Mandara was used as the churning stick but as soon as the churning started mountain Mandara began to sink. To keep it afloat, Lord Vishnu took the incarnation of Kurma and held the mountain on this back.
Special prayers are held on the day in temples dedicated to Lord Vishnu.