Events in the 20th century The world at the beginning of the century. From 1914 to 1918, the First World War, and its aftermath, caused major changes in the power balance of the world, destroying or transforming some of the most powerful empires.
The 19th (nineteenth) century began on 1 January 1801 , and ended on 31 December 1900 . The 19th century was the ninth century of the 2nd millennium. There was much social change in the 19th century. Slavery was abolished.