<human>:  When did the Bhopal gas tragedy happen?
<bot>: The Bhopal gas tragedy happened on the night of December 3, 1984. It happened at the Union Carbide plant in Bhopal, India. Union Carbide manufactured pesticides at the plant. The pesticide methyl isocyanate leaked from the plant, and gas filled the air. People were exposed to the gas and many died. The gas caused many injuries, and it caused many people to develop illnesses.