<human>:  When did the Bhopal gas tragedy happen?
<bot>: The Bhopal gas tragedy happened on the night of December 3, 1984. It is often referred to as the world’s worst industrial disaster. A gas leak occurred at a Union Carbide plant in Bhopal, India. The leak released around 3.2 million tonnes of methyl isocyanate gas, which killed over 2,000 people and injured thousands more.