| 107551 | September 19 | Holiday and observance | International Talk Like a Pirate Day |
| 107552 | September 20 | Event | 622 – Muhammad and Abu Bakr arrived in Medina |
| 107553 | September 20 | Event | 1058 – Agnes of Poitou and Andrew I of Hungary meet to negotiate about the border-zone in present-day Burgenland. |
| 107554 | September 20 | Event | 1066 – Battle of Fulford, Viking Harald Hardrada defeats earls Morcar and Edwin |
| 107555 | September 20 | Event | 1187 – Saladin begins the Siege of Jerusalem. |
| 107556 | September 20 | Event | 1260 – the Great Prussian Uprising among the old Prussians begins against the Teutonic Knights. |
| 107557 | September 20 | Event | 1378 – Cardinal Robert of Geneva, called by some the "Butcher of Cesena", is elected as Avignon Pope Clement VII, beginning the Papal schism. |
| 107558 | September 20 | Event | 1498 – The 1498 Nankai earthquake generates a tsunami that washes away the building housing the statue of the Great Buddha at Kōtoku-in in Kamakura, Kanagawa, Japan since then the Buddha has sat in the open air. |
| 107559 | September 20 | Event | 1519 – Ferdinand Magellan sets sail from Sanlúcar de Barrameda with about 270 men on his expedition to circumnavigate the globe. |
| 107560 | September 20 | Event | 1596 – Diego de Montemayor founds the city of Monterrey in New Spain. |
| 107561 | September 20 | Event | 1697 – The Treaty of Ryswick is signed by France, England, Spain, the Holy Roman Empire and the Dutch Republic ending the Nine Years' War (1688–97). |
| 107562 | September 20 | Event | 1737 – The finish of the Walking Purchase which forces the cession of 1.2 million acres (4,860 km²) of Lenape-Delaware tribal land to the Pennsylvania Colony. |
| 107563 | September 20 | Event | 1792 – French troops stop allied invasion of France, during the War of the First Coalition at Valmy. |
| 107564 | September 20 | Event | 1835 – Ragamuffin rebels capture Porto Alegre, then capital of the Brazilian imperial province of Rio Grande do Sul, triggering the start of ten-year-long Ragamuffin War. |
| 107565 | September 20 | Event | 1848 – The American Association for the Advancement of Science is created. |
| 107566 | September 20 | Event | 1854 – Battle of Alma: British and French troops defeat Russians in Crimea. |
| 107567 | September 20 | Event | 1857 – The Indian Rebellion of 1857 ends with the recapture of Delhi by troops loyal to the East India Company. |
| 107568 | September 20 | Event | 1860 – The Prince of Wales (later King Edward VII of the United Kingdom) visits the United States. |
| 107569 | September 20 | Event | 1863 – American Civil War: The conclusion of the Battle of Chickamauga in northwestern Georgia, the bloodiest two-day battle of the conflict, and the only significant Confederate victory in the war's Western Theater. |
| 107570 | September 20 | Event | 1870 – Bersaglieri corps enter Rome through the Porta Pia and complete the unification of Italy, ending de facto the temporal power of popes. |
| 107571 | September 20 | Event | 1871 – Bishop John Coleridge Patteson is martyred on the island of Nukapu, a Polynesian outlier island now in the Temotu Province of the Solomon Islands. He is the first bishop of Melanesia. |
| 107572 | September 20 | Event | 1881 – U.S. President Chester A. Arthur is sworn in, the morning after becoming President upon James A. Garfield's death. |
| 107573 | September 20 | Event | 1893 – Charles Duryea and his brother road-test the first American-made gasoline-powered automobile. |
| 107574 | September 20 | Event | 1906 – Cunard Line's RMS Mauretania is launched at the Swan Hunter & Wigham Richardson shipyard in Newcastle upon Tyne, England. |
| 107575 | September 20 | Event | 1909 – The Parliament of the United Kingdom passes the South Africa Act 1909, creating the Union of South Africa from the British Colonies of the Cape of Good Hope, Natal, Orange River Colony, and the Transvaal Colony. |
| 107576 | September 20 | Event | 1910 – The ocean liner SS France, later known as the "Versailles of the Atlantic", is launched. |
| 107577 | September 20 | Event | 1911 – White Star Line's RMS Olympic collides with British warship HMS Hawke. |
| 107578 | September 20 | Event | 1920 – Foundation of the Spanish Legion. |
| 107579 | September 20 | Event | 1930 – Syro-Malankara Catholic Church is formed by Archbishop Mar Ivanios. |
| 107580 | September 20 | Event | 1942 – Holocaust in Letychiv, Ukraine. In the course of two days the German SS murders at least 3,000 Jews. |