Kartik Purnima is celebrated on the Purnima (Full moon) day or the fifteenth lunar day of Kartika (November- December). It is also known as Tripuri Purnima and Tripurari Purnima.
Legends: Tripurari Purnima derives its name from Tripurari (God Shiva) the foe of Tripurasura. Tripurasura had conquered the whole world and defeated the Gods and had created 3 cities in space together called Tripura. Lord Shiva killed the demons (Tripurasura and his 3 sons) and destroyed the 3 cities with a single arrow. Gods overjoyed with victory declared the day as festival of illuminations. Thus this day is also celebrated as Deva Deepavali- the festival of Light of Gods.
Kartika Purnima is also birth day of Matsya Avatar, the fish incarnation of Vishnu. Kartik Purnima is the last day to perform "Tulsi Vivah". It is also the birth day of Vrinda, the personification of Tulsi Plant and of Karthikeya the God of Warand the son of Lord Shiva.
Rituals: It is believed that Matsya Avatar, the Vishnu incarnation protected Manu, the first man from Mahaprakya (deluge) on this day. A sacred bath in the morning "Karthik Snana" and a bath during moon rise and worship by way of six prayers such as Shiva Sambuti, Satait and so further are the highlights of the celebration. Himsa is prohibited on this day which includes shaving, haircutting, cutting of trees, plucking of fruits &flowers and cutting of crop. Charity like donation of cows, feeding of Brahmins and fasting are few of the activities prescribed for the day. Giving gift of gold is said to fulfil all desires of people.
Tripuri Purnima is only next to "Mahasivaratri" amongst festivals dedicated to Lord Shiva.
People place 360 or 720 wicks in temples to secure escape from reaching hell after death. Lights are floated in water and lit under the tree to help fish & birds to attain salvation.
"Shiva Linga Mahajala Abhishekam"is observed on this day.
On Kartik Purnima day Gods descend on earth and reside in several rivers. Kartika Purnima is celebrated as Maritime Glory day of Odisha with "Boita Bandana" and Kartikeswar Puja. Most people in Odisha do not consume non-vegetarian dishes and last five days of Kartika month is observed as "Punchuka" culminating with Purnima. Devotees visit temples in large number and try to partake with Mahaprasad in Lord Jagannath Temple on the Purnima day if possible to earn "Punnya".