The Ottoman Empire signed the Treaty of Adrianople with Russia, which ended the Russo-Turkish War.
Source
14-year-old Ahmed Mohamed was arrested at school after bringing in a homemade clock, which was mistaken for a bomb.
Hindi became the official language of India.
The Vought-Sikorsky VS-300 became the first successful helicopter to fly.
The people of Estonia voted to approve joining the European Union.
Pope Paul VI canonized Elizabeth Anne Seton as the first American saint.