1500: Pedro Álvares Cabral is the first European to discover Brazil, landing near Monte Pascoal, claims it for Portugal

1915: First military use of poison gas occurs when Germany uses chlorine gas against the Allies at Ypres in World War I [1]
1993: Holocaust Memorial Museum dedicated in Washington, D.C.

1994: 7,000 Tutsi slaughtered by Hutus in the stadium at Kibuye, Rwanda

2006: Nepali security forces open fire on Pro-democracy protesters demonstrating against King Gyanendra, injuring hundreds. The protesters go on to secure the restoration of Parliament and a federal state.

2016: Paris Agreement on climate change signed in New York binding 195 nations to an increase in the global average temperature to less than 2°C above pre-industrial levels and to pursue efforts to limit the increase to 1.5°C

Source: Onthisday.com