Balarama Purnima is the auspicious appearance day of Lord Balarama, the elder brother of Lord Sri Krishna. In 2016, Balarama Purnima date is August 18. It is celebrated on Shravana Purnima, the full moon day in Shravana month.
Lord Krishna and Balarama are not two different Personalities of Godhead. God is one without a second, but He expands Himself in many forms without their being separate from one another. They are all plenary expansions. The immediate expansion of Lord Krishna is Balarama. Lord Balarama is as good as Krishna Himself, the only difference being that the bodily hue of Krishna is dark and that of Balarama is fair.
Lord Balarama is the source of all spiritual power (bala) which helps one attain the highest bliss of life (ramana) and hence the name Balarama. He is the protector of the devotees of the Lord. Without His mercy one cannot approach the Supreme Lord Sri Krishna.
ISKCON Bangalore celebrates this festival every year with grand Abhisheka for Their Lordships Sri Sri Krishna Balarama, followed by a grand offering of 56 items (Chappan-Bhoga).