Portugal
On 1 February 1908, the king Dom Carlos I of Portugal and his heir apparent, Prince Royal Dom Luís Filipe, Duke of Braganza, were murdered in Lisbon. Under his rule, Portugal had twice been declared bankrupt – on 14 June 1892, and again on 10 May 1902 – causing social turmoil, economic disturbances, protests, revolts and criticism of the monarchy. Manuel II of Portugal became the new king, but was eventually overthrown by the 5 October 1910 revolution, which abolished the regime and instated republicanism in Portugal. Political instability and economic weaknesses were fertile ground for chaos and unrest during the Portuguese First Republic. These conditions would lead to the failed Monarchy of the North, 28 May 1926 coup d'état, and the creation of the National Dictatorship (Ditadura Nacional).

Q: On what day were King Dom Carlos I and and his heir, Prince Royal Dom Luis Filipe, Duke of Braganza, murdered?
1 February 1908