Damodar Dwadashi Vrat Shukla Paksha Pavitra Ekadasi Vrat दामोदर द्वादशी

Damodar Dwadashi, or Damodara Dwadasi, is observed on the 12th day of the waxing phase of moon (Shukla Paksha) of Shravan month. In 2016, the date of Damodar Dwadashi is August 15 and is dedicated to Lord Krishna. The previous day is observed as Pavitra Ekadasi Vrat. Damodara is one among the numerous names of Lord Krishna and Dwadashi is the 12th day of a lunar fortnight in Hindu calendar.

Some people continue the Ekadasi fasting (observed on the 11th day) to Damodar Dwadashi. On the Dwadasi day, it is not a complete fast but people avoid all types of grains and beans.

Damodar Dwadashi Vrat is more popular in North India and with staunch followers of Vaishnavaism.
Generally, Dwadashi is dedicated to Lord Vishnu and devout Hindus break the Ekadasi fast on the morning of Dwadashi.

source: hindu-blog.com