Wikipedia:Selected anniversaries/April 13
- 1598 - King Henry IV of France issued the Edict of Nantes, allowing freedom of religion to the Huguenots.
- 1883 - Alferd Packer was convicted of cannibalism.
- 1919 - British and Gurkha troops opened fire on a peaceful political gathering in Amritsar, Punjab in India, killing hundreds of Sikhs, Hindus and Muslims.
- 1943 - World War II: The discovery of a mass grave of Polish prisoners-of-war executed by Soviet forces in the Katyń Forest Massacre was announced in Germany, driving a wedge among the Allies, particularly the Polish government-in-exile in London and the Soviet Union.