| 8551 | January 19 | Holiday and observance | Theophany / Epiphany (Eastern and Oriental Orthodoxy), and its related observances:Timkat, or 20 during Leap Year (Ethiopian Orthodox)Vodici or Baptism of Jesus (Republic of Macedonia) |
| 8552 | January 20 | Event | 250 – Emperor Decius begins a widespread persecution of Christians in Rome. Pope Fabian is martyred. |
| 8553 | January 20 | Event | 649 – King Chindasuinth, at the urging of bishop Braulio of Zaragoza, crowns his son Recceswinth as co-ruler of the Visigothic Kingdom. |
| 8554 | January 20 | Event | 1265 – The first English parliament to include not only Lords but also representatives of the major towns holds its first meeting in the Palace of Westminster, now commonly known as the "Houses of Parliament". |
| 8555 | January 20 | Event | 1320 – Duke Wladyslaw Lokietek becomes king of Poland. |
| 8556 | January 20 | Event | 1356 – Edward Balliol abdicates as King of Scotland. |
| 8557 | January 20 | Event | 1523 – Christian II is forced to abdicate as King of Denmark and Norway. |
| 8558 | January 20 | Event | 1567 – Battle of Rio de Janeiro: Portuguese forces under the command of Estácio de Sá definitively drive the French out of Rio de Janeiro. |
| 8559 | January 20 | Event | 1576 – The Mexican city of León is founded by order of the viceroy Don Martín Enríquez de Almanza. |
| 8560 | January 20 | Event | 1649 – Charles I of England goes on trial for treason and other "high crimes". |
| 8561 | January 20 | Event | 1783 – The Kingdom of Great Britain signs a peace treaty with France and Spain, officially ending hostilities in the American Revolutionary War (also known as the American War of Independence). |
| 8562 | January 20 | Event | 1785 – Invading Siamese forces attempt to exploit the political chaos in Vietnam, but are ambushed and annihilated at the Mekong river by the Tây Sơn in the Battle of Rạch Gầm-Xoài Mút. |
| 8563 | January 20 | Event | 1788 – The third and main part of First Fleet arrives at Botany Bay. Arthur Phillip decides that Botany Bay is unsuitable for the location of a penal colony, and decides to move to Port Jackson. |
| 8564 | January 20 | Event | 1839 – In the Battle of Yungay, Chile defeats an alliance between Peru and Bolivia. |
| 8565 | January 20 | Event | 1841 – Hong Kong Island is occupied by the British. |
| 8566 | January 20 | Event | 1877 – Last day of the Constantinople Conference which resulted in agreement for political reforms in the Balkans. |
| 8567 | January 20 | Event | 1887 – The United States Senate allows the Navy to lease Pearl Harbor as a naval base. |
| 8568 | January 20 | Event | 1920 – The American Civil Liberties Union is founded. |
| 8569 | January 20 | Event | 1921 – The first Constitution of Turkey is adopted, making fundamental changes in the source and exercise of sovereignty by consecrating the principle of national sovereignty. |
| 8570 | January 20 | Event | 1929 – In Old Arizona, the first full-length talking motion picture filmed outdoors, is released. |
| 8571 | January 20 | Event | 1936 – Edward VIII becomes King of the United Kingdom. |
| 8572 | January 20 | Event | 1941 – A German officer is murdered in Bucharest, Romania, sparking a rebellion and pogrom by the Iron Guard, killing 125 Jews and 30 soldiers. |
| 8573 | January 20 | Event | 1942 – World War II: At the Wannsee Conference held in the Berlin suburb of Wannsee, senior Nazi German officials discuss the implementation of the "Final Solution to the Jewish question". |
| 8574 | January 20 | Event | 1945 – World War II: The Miklós provisional government of Hungary agrees to an armistice with the Allies. |
| 8575 | January 20 | Event | 1945 – World War II: Germany begins the evacuation of 1.8 million people from East Prussia, a task which will take nearly two months. |
| 8576 | January 20 | Event | 1949 – Point Four Program a program for economic aid to poor countries announced by United States President Harry S. Truman in his inaugural address for a full term as President. |
| 8577 | January 20 | Event | 1954 – In the United States, the National Negro Network is established with 40 charter member radio stations. |
| 8578 | January 20 | Event | 1959 – The first flight of the Vickers Vanguard. |
| 8579 | January 20 | Event | 1960 – Hendrik Verwoerd announces a plebiscite on whether South Africa should become a Republic. |
| 8580 | January 20 | Event | 1969 – East Pakistani police kill student activist Amanullah Asaduzzaman. The resulting outrage is in part responsible for the Bangladesh Liberation War. |