Vaikhanasa Deepam is observed on the Karthigai Pournami day as per tamil calendar. In 2016, Vaikhanasa Deepam date is December 13.
Karthigai Pournami or the full moon day in the tamil karthigai masam is highly auspicious in South India. This day is also celebrated as Karthigai Deepam.
Vaikhanasa is an important sect in Hinduism and follows Vishnu and his various avatars. It is believed that Sage Vaikanasa is the human form of Lord Vishnu aroused from his mind and as per his instructions, Vaikhanasa preached the Vaikhanasa Bhagavath Shastras to his disciples Bhrugu, Mareechi , Atri and Kashyapa. Sri Vaikanasa Agamas are a compilation of several lakhs of slokas which he taught to his disciples.
Vaikhanasa Deepam is observed by lighting bonfore known as Sokkappanai in the temples. The legend associated with this festival is based on the incarnation of Lord Vishnu as Vamana. It is believed that the three steps which Vamana took are based on the movement of sun and earth.
It is said that the two steps of Vamana are the Uttarayana and Venal Equinox. And the third step which sends Bali to the patala loka is the autumn equinox. To commemorate this event the Vaikhanasa Deepam is celebrated.