<human>:  When did Nelson Mandela die?
<bot>: Nelson Mandela died in 2013 at the age of 95. He was a leader of the African National Congress, which was the main political party in South Africa during the apartheid era. He was imprisoned for 27 years for his political activities, and was released in 1990. He was elected president of South Africa in 1994, and served until 1999.