When was Bangladesh founded?

Constitutionally, Bangladesh was founded on 26 March, 1971 after it had been a part of Pakistan for 24 years. On 25 March, 1971, Pakistan invaded the then East Pakistan (Bangladesh) and killed thousands of people there. As a result, East Pakistan responded with the proclamation of independence on 26 March, 1971. Since then, until 16 December Bangladesh had remained at war with Pakistan's invading forces for 9 months before Pakistani troops surrendered on 16 December, 1971.

Thus, Bangladesh was founded on 26 March, 1971 as a state. But it gained actual freedom and sovereignty on 16 December, 1971.