Dwadashaditya Vrata (Dwadasha Aditya Vratam) is observed on Dwadashi day in the bright half during Margashirsha Month. In 2016, Dwadashaditya Vrata date is December 11.
Dwadashaditya Vrata is dedicated to worship Lord Surya (Surya Deva) and Lord Krishna. It is observed as three-phases for a year. It is less popular vrata mainly observed by Vaishnava sect of people.
During the first four months (first phase) of the vrata, five pots filled with rice and other food grains are offered to Brahmins. During the second phase of four months, a pot full of dry nuts or dry grams are donated from Chaitra month. In the final phase of four months, ghee is offered to Brahmins.
The first phase of Akhanda Dwadashi vratam – Margasira, Paush, Magh and Phalgun months. The second phase of the vrata – Chaitra, Vaisakh, Jyeshta and Ashada months. The final or the third phase of the vratha – Shravan, Bhadrapad, Ashwin and Karthik months.
When it comes to the Surya Puja, in each month Surya Bhagavan is considered with a particular name which signifies the intensity of his light and heat. Dwadasha Aditya Vrata begins on Margashirsha Dwadashi day continues for a year.