In July 1971, Indian Prime Minister Indira Gandhi openly referred to former East Pakistan as Bangladesh. Some Pakistani and Indian officials continued to use the name "East Pakistan" until 16 December 1971.

December 16 is a significant day for India and its neighbours Bangladesh and Pakistan. In 1971, India won the war against Pakistan that resulted in the birth of Bangladesh (then East Pakistan). On this day 47 years ago, Pakistan lost half its country, its forces in the East, and had to publicly surrender to India.

The Bangladesh Liberation War, also known as the Bangladesh War of Independence, or simply the Liberation War in Bangladesh, was a revolution and armed conflict sparked by the rise of the Bengali nationalist and self-determination movement in what was then East Pakistan during the 1971 Bangladesh genocide. Wikipedia