<human>:  When did the Bhopal gas tragedy happen?
<bot>: The Bhopal gas tragedy happened on the night of December 3, 1984. It was a major industrial accident that occurred in the city of Bhopal, India. The accident occurred when a pesticide plant owned by Union Carbide Corporation leaked methyl isocyanate gas into the atmosphere. The leak killed more than 2,000 people, and affected hundreds of thousands of others. The incident is considered to be one of the worst industrial disasters in history.