Reuters historical calendar - April 21

London, Apr 20 (Reuters) Following are some of the major events to have occurred on April 21 since 1900: 1910 - American novelist Mark Twain (Samuel Langhorne Clemens) died. His masterpieces ''The Adventures of Tom Sawyer'' and ''The Adventures of Huckleberry Finn'' are drawn from his boyhood experiences.

1918 - Baron Manfred von Richthofen, Germany's top aviator in World War One, was killed in action. Known as ''The Red Baron'', he shot down 80 enemy aircraft.

1960 - Brasilia became Brazil's new capital.

1967 - A military coup in Athens established the regime of the ''Greek Colonels''.

1971 - Francois ''Papa Doc'' Duvalier, president of Haiti since 1957, died. He ran the country as a dictatorship and created a gangster militia known as the Tontons Macoutes.

1975 - South Vietnamese President Nguyen Van Thieu resigned as Viet Cong forces closed on his capital, Saigon.

1985 - Tancredo Neves, Brazilian president-elect, died on the eve of his swearing-in.

1989 - Tens of thousands of students and workers poured into Beijing's Tiananmen Square in defiance of official warnings against anti-government protests.

1990 - Erte (Romain de Tirtoff), prolific Russian-born Art Deco designer, died. He created the 1920s theatre sets for America's Ziegfield Follies and France's Folies Bergeres.

1993 - Bolivia's Supreme Court sentenced former dictator General Luis Garcia Meza to 30 years in jail for crimes ranging from mass murder and torture to wholesale fraud against the state.

1999 - NATO warplanes blasted Yugoslav President Slobodan Milosevic's party headquarters in Belgrade.

2002 - Thousands took to the streets to protest the shock triumph of far right leader Jean-Marie Le Pen in first round of French presidential elections.

2003 - Nina Simone, U.S. blues and jazz singer, died. Her smoky tones gave voice to the American civil rights movement and ranged from gospel to George Gershwin. She was 70.

2004 - Nuclear whistleblower Mordechai Vanunu was freed from prison in Israel after 18 years, saying he was proud of revealing secrets that exposed the Jewish state as an atomic power.

2005 - Zhang Chunqiao, a member of China's notorious Gang of Four led by the wife of Chairman Mao Zedong, died aged 88.

REUTERS CH DS1156