| Event | (1)0s or (2)0s |
|---|
| World population reached 2 billion | |
| First use of poison gas on the battlefield | |
| Pahlavi Dynasty rose to power in Iran | |
| Implementation of Daylight saving time | |
| Türkiye became a secular republic | |
| Tsar Nicholas II and his family murdered | |
| Northern Ireland created within the UK | |
| Mussolini formed National Fascist Party | |
| Gandhi launched non-cooperation movement | |
| Adolf Hitler became Führer of the Nazi Party | |
| Vladimir Lenin died | |
| Grigory Rasputin assassinated | |
| Hirohito became Emperor of Japan | |
| Union of South Africa created | |
| Vatican City recognized as a sovereign state | |
| Treaty of Versailles | |
| Mexican Revolution began | |
| Stalin became leader of the Soviet Union | |
| Franz Ferdinand assassinated | |
| 'Mein Kampf' published | |
| Arizona admitted to the Union | |
| Walt Disney Company founded | |
| Mark Twain died | |
| Roald Amundsen reached the South Pole | |
| Egypt gained independence from the UK | |
| Bubble gum invented | |
| RMS Lusitania sunk | |
| Ernest Rutherford discovered the proton | |
| Soviet Union formed | |
| Armenian genocide in the Ottoman Empire started | |
| World population reached 2 billion | |
| First use of poison gas on the battlefield | |
| Pahlavi Dynasty rose to power in Iran | |
| Implementation of Daylight saving time | |
| Türkiye became a secular republic | |
| Tsar Nicholas II and his family murdered | |
| Northern Ireland created within the UK | |
| Mussolini formed National Fascist Party | |
| Gandhi launched non-cooperation movement | |
| Adolf Hitler became Führer of the Nazi Party | |
| Vladimir Lenin died | |
| Grigory Rasputin assassinated | |
| Hirohito became Emperor of Japan | |
| Union of South Africa created | |
| Vatican City recognized as a sovereign state | |
