What started on the first of January, 1901?

What started on January 1, 1901? The 20th century. Under the Gregorian calendar, the 20th century ran from January 1, 1901, through December 31, 2000. It was the tenth century of the Common Era and the final century of the second millennium.

The date sometimes surprises people because the year 1900 is often casually treated as the beginning of the 20th century. However, the traditional calendar has no year zero: the first century covered years 1 through 100, so the 20th century began with year 1901. The 1900s, by contrast, were the decade from 1900 through 1909.

The century brought two world wars, the Russian Revolution, the Cold War, space exploration, nuclear power, commercial aviation, television, and the transformation from analog to digital computing. Its population grew from roughly 1.6 billion to more than 6 billion.

January 1, 1901, also marked the creation of the Commonwealth of Australia through the federation of several British colonies, making the date significant for both calendar history and world history.