| 1 January 1068 | Byzantine Empire [administration] | Romanus IV Diogenes, who has married the empress Eudocia Macrembolitissa, is crowned as Byzantine emperor. |
| 1 January 1077 | Holy Roman Empire [political events] | King Henry IV of Germany submits to Pope Gregory VII at Canossa and is absolved from excommunication. |
| 1 January 1160 | Almohad Emirate, Sicily, North Africa [revolution] | The fall of Mahdiyah (in modern Tunisia) to local rebels completes the loss of all the conquests of the kings of Sicily in North Africa. |
| 1 January 1188 | England, France [diplomacy] | King Henry II of England and King Philip II of France, meeting at Gisors, France, to discuss a truce, are persuaded to make peace and go on crusade; they impose ‘Saladin tithes’ to finance their expeditions. |
| 1 January 1204 | Byzantine Empire [political events] | An anti-Latin mob in Constantinople murders the Byzantine emperor Isaac II Angelus and proclaims Nicholas Canabus as emperor. |
| 1 January 1207 | Holy Roman Empire, Germany, England [political events] | Philip, Duke of Swabia and ‘king of the Romans’ (king of Germany), takes the city of Cologne, so achieving a dominant position in Germany; his rival king, Otto IV, flees through Denmark to England. |
| 1 January 1246 | Provence, France [political events] | Provence becomes part of France with the marriage of Beatrice, heiress of Count Raymond Berengar IV (who died in 1245), to Charles, count of Anjou, the brother of King Louis IX of France. |
| 1 January 1279 | Portugal [administration] | King Afonso III of Portugal dies. He is succeeded by his son Dinis. |
| 1 January 1294 | England, France [political events] | King Edward I of England responds to his summons, by proxy, to the Parlement of Paris to answer for attacks by Anglo-Gascons on French seamen, and agrees to surrender castles in Gascony during an enquiry. The consequent French seizure of Gascony leads to war between the two countries. |
| 1 January 1409 | Wales, England [wars] | The Welsh rebels holding Harlech Castle surrender to the English. The rebellion of Owen Glendower, Prince of Wales, has now collapsed. |
| 1 January 1449 | Italy [births and deaths] | Lorenzo de' Medici the Magnificent, statesman and ruler of Florence 1453–92, born in Florence, Italy (–1492). |
| 1 January 1660 | England [thought and scholarship] | English diarist Samuel Pepys begins his Diary, which he keeps until May 1669. |
| 1 January 1673 | North America [postal services] | The first regular mounted mail service is begun, between New York City and Boston, Massachusetts. The trip takes three weeks, with the rider changing horses along the way at scattered posts. This road, the Boston Post Road, is the first of many post roads in the North American colonies. |
| 1 January 1704 | Poland, Saxony, Holy Roman Empire, Germany, Sweden [Great Northern War (1700–21)] | King Augustus II of Poland, known to history as Augustus the Strong, who is also the hereditary elector of Saxony as Frederick Augustus I and the occupant of the Polish throne supported by the anti-Swedish coalition, is deposed because of Swedish military success in Poland. |
| 1 January 1707 | Portugal [political events] | João V, regent of Portugal in 1704 and 1705, succeeds to the throne following the death of his father Pedro II. |
| 1 January 1801 | UK [legislation] | The Act of Union creates the United Kingdom of Great Britain and Ireland, bringing Ireland under direct control of the Parliament in Westminster. |
| 1 January 1820 | Spain [revolution] | A revolution begins in Spain due to King Ferdinand VII's failure to adhere to the constitution of 1812 and his sending of troops to South America to put down risings in the Spanish colonies that have attracted much popular support in Spain itself. |
| 1 January 1863 | France [births and deaths] | Pierre, Baron de Coubertin, French administrator responsible for the revival of the Olympic Games and who serves as the first president of the International Olympic Committee 1896–1925, born in Paris, France (–1937). |
| 1 January 1876 | France [weights and measures] | The International System of Weights and Measures comes into effect in France. |
| 1 January 1877 | UK, India [political events] | Queen Victoria of Britain is proclaimed empress of India. |
| 1 January 1886 | Burma, UK [colonization] | Britain annexes Upper Burma, though guerrilla warfare continues. |
| 1 January 1901 | Australia [political events] | The Commonwealth of Australia comes into being, with the federalist and protectionist Edmund Barton as prime minister. |
| 1 January 1909 | United Kingdom [welfare] | The first old-age pensions are paid out by the government in Britain.These are noncontributory: the payment is small and made on a restricted basis at the age of 70. |
| 1 January 1941 | USA [television] | The Columbia Broadcasting System (CBS) begins regular television broadcasting (in competition with NBC). |
| 1 January 1948 | Europe [trade] | The Benelux Customs Union comes into effect, creating a free-trade zone between Belgium, the Netherlands, and Luxembourg. It is a significant step towards closer European integration. |
| 1 January 1951 | UK [cinema and film] | The British Board of Film Censors introduces the ‘X’ classification, to identify films unsuitable for those under 16. |
| 1 January 1951 | North Korea, South Korea, China [Korean War (1950–53)] | In the Korean War, North Korean and Chinese forces break United Nations (UN) lines on the 38th parallel and, on 4 January, take Seoul, capital of South Korea. |
| 1 January 1953 | Maldives [decolonization] | The Maldive Islands become independent under British protection. The new president, Amin Didi, plays centre forward in a ceremonial football match. |
| 1 January 1954 | UK [motor vehicles] | Flashing directional indicator lights are made compulsory on cars in Britain. |
| 1 January 1959 | Cuba [revolution] | The Cuban guerrilla campaign of the 26 July Movement forces General Fulgencio Batista to resign and flee to Dominica. A military junta appoints Carlos Piedra as provisional president. |
| 1 January 1960 | Cameroon [decolonization] | French Cameroon becomes the independent Republic of Cameroon. |
| 1 January 1961 | UK [family planning] | The first oral contraceptive pill, Conovid, goes on sale in Britain, manufactured by the British firm G D Searle. From 4 December, it is available on the NHS. |
| 1 January 1962 | Pacific, Samoa [political events] | Western Samoa, previously administered by New Zealand, becomes the first sovereign independent Polynesian state. |
| 1 January 1973 | UK, Ireland, Denmark [political events] | Britain, Ireland, and Denmark become members of the European Economic Community (Common Market). |
| 1 January 1981 | Greece [political events] | Greece becomes the 10th member of the European Community. |
| 1 January 1984 | Brunei [decolonization] | The sultanate of Brunei becomes independent after 95 years as a British protectorate. |
| 1 January 1985 | UK [telephone services] | Racal-Vodaphone introduces the first mobile phones in Britain. |
| 1 January 1986 | Europe [political events] | Spain and Portugal become the 11th and 12th members of the European Community. |
| 1 January 1993 | Europe [political events] | The European Community's single market comes into force, establishing the free movement of goods, capital, and services across national borders, with some restrictions. |
| 1 January 1993 | Czech Republic, Slovak Republic [political events] | The Czech and Slovak republics become separate sovereign countries. |
| 1 January 1994 | Europe [political events] | The second stage of economic and monetary union in Europe comes into force with the establishment of the European Economic Area, incorporating European Free Trade Association (EFTA) members (except Switzerland and Liechtenstein) into the European Union (EU) free market. |
| 1 January 1995 | Argentina, Brazil, Paraguay, Uruguay [political events] | The Southern Common Market or Mercosur, the world's fourth-largest free-trade grouping comprising Argentina, Brazil, Paraguay, and Uruguay, comes into existence. |
| 1 January 1995 | Austria, Finland, Sweden, Europe [political events] | Austria, Finland, and Sweden join the European Union (EU), increasing the Union's population from 345 million to 368 million. |
| 1 January 1998 | UK [poetry] | The Times newspaper, of London, England, begins serializing a group of previously unpublished poems by British poet Ted Hughes about his late wife, US poet Sylvia Plath. |
| 1 January 1999 | Europe [economics] | The single European currency, the euro, is launched in 11 participating European Union (EU) countries: Austria, Belgium, Finland, France, Germany, Ireland, Italy, Luxembourg, the Netherlands, Portugal, and Spain. It performs strongly when trading begins on 4 January. |
| 1 January 2000 | [everyday life] | The new millennium is celebrated across the world, with fireworks, street parties, ceremonies, and speeches. The millennium bug does not appear to make a large impact, and despite fears of acts of extremism and terrorism, the global celebration passes peacefully. |
| 1 January 2000 | UK [other structures] | The Millennium Dome in Greenwich, London, England, opens to the public, and is scheduled to remain open throughout 2000. Some 12,500 people visit it on the opening day. |
| 1 January 2002 | [banking and finance] | The single European currency becomes a reality in 12 member states of the European Union as euro notes and coins are introduced officially to replace national currencies. The United Kingdom, Denmark, and Sweden remain outside the eurozone. |
| 1 January 2003 | England [Crimean War (1854–56)] | The killing of two teenage bystanders – Charlene Ellis and Latisha Shakespear – outside a New Year's party venue in Birmingham, England, in an apparent shootout between rival black gangs focuses attention on the growing problem of gun crime in UK inner cities. |
| 1 January 2007 | [international organizations] | Ban Ki-moon, South Korea's former foreign minister, takes office as the new United Nations secretary-general in succession to Kofi Annan. |
| 1 January 2007 | Romania Bulgaria [international organizations] | Romania and Bulgaria become the European Union's 26th and 27th member states. |
