13 April 1992
Just two years after coming out from prison, Nelson Mandela announced his intention to separate from his wife of 34 years, Winnie Madikizela-Mandela.  Mandela and Madikizela-Mandela were married in 1958, having met the previous year. The couple had two daughters, Zenani born in 1959 and Zindzi born in 1960. In 1962, Mandela was arrested and sentenced to life imprisonment on Robben Island. The couple were re-united in 1990 after Mandela's release, however, they eventually separated. The divorce was finalised in 1996. While Madikizela-Mandela never remarried, Mandela went on to marry the  former first lady of Mozambique, Graca Machel in 1998.
References

Smith D.(2013), Nelson and Winnie Mandela's marriage ended, but the bond was never broken from The Guardian , 6 December, [online] Available at: www.theguardian.com [Accessed: 11 April 2014]|Frontline "The Separation" BOOK EXCERPT from Frontline [online] Available at: www.pbs.org [Accessed: 11 April 2014]