| 1 | January 1 | Event | 153 BC – Roman consuls begin their year in office. |
| 2 | January 1 | Event | 45 BC – The Julian calendar takes effect as the civil calendar of the Roman Empire, establishing January 1 as the new date of the new year. |
| 3 | January 1 | Event | 42 BC – The Roman Senate posthumously deifies Julius Caesar |
| 4 | January 1 | Event | 69 – The Roman legions in Germania Superior refuse to swear loyalty to Galba. They rebel and proclaim Vitellius as emperor. |
| 5 | January 1 | Event | 193 – The Senate chooses Pertinax against his will to succeed Commodus as Roman emperor. |
| 6 | January 1 | Event | 404 – An infuriated Roman mob tears Telemachus, a Christian monk, to pieces for trying to stop a gladiators' fight in the public arena held in Rome. |
| 7 | January 1 | Event | 414 – Galla Placidia, half-sister of Emperor Honorius, is married to the Visigothic king Ataulf at Narbonne. The wedding is celebrated with Roman festivities and magnificent gifts from the Gothic booty. |
| 8 | January 1 | Event | 417 – Emperor Honorius forces Galla Placidia into marriage to Constantius, his famous general (magister militum). |
| 9 | January 1 | Event | 1001 – Grand Prince Stephen I of Hungary is named the first King of Hungary by Pope Sylvester II. |
| 10 | January 1 | Event | 1068 – Romanos IV Diogenes marries Eudokia Makrembolitissa and is crowned Byzantine Emperor. |
| 11 | January 1 | Event | 1259 – Michael VIII Palaiologos is proclaimed co-emperor of the Empire of Nicaea with his ward John IV Laskaris. |
| 12 | January 1 | Event | 1438 – Albert II of Habsburg is crowned King of Hungary. |
| 13 | January 1 | Event | 1502 – The present-day location of Rio de Janeiro, Brazil is first explored by the Portuguese. |
| 14 | January 1 | Event | 1515 – King Francis I of France succeeds to the French throne. |
| 15 | January 1 | Event | 1527 – Croatian nobles elect Ferdinand I of Austria as King of Croatia in the Parliament on Cetin. |
| 16 | January 1 | Event | 1600 – Scotland begins its numbered year on January 1 instead of March 25. |
| 17 | January 1 | Event | 1651 – Charles II is crowned King of Scotland. |
| 18 | January 1 | Event | 1700 – Russia begins using the Anno Domini era and no longer uses the Anno Mundi era of the Byzantine Empire. |
| 19 | January 1 | Event | 1707 – John V is crowned King of Portugal. |
| 20 | January 1 | Event | 1739 – Bouvet Island is discovered by French explorer Jean-Baptiste Charles Bouvet de Lozier. |
| 21 | January 1 | Event | 1772 – The first traveler's cheques, which can be used in 90 European cities, go on sale in London, England. |
| 22 | January 1 | Event | 1773 – The hymn that became known as "Amazing Grace", then titled "1 Chronicles 17:16–17" is first used to accompany a sermon led by John Newton in the town of Olney, England. |
| 23 | January 1 | Event | 1776 – American Revolutionary War: Norfolk, Virginia is burned by combined Royal Navy and Continental Army action. |
| 24 | January 1 | Event | 1781 – American Revolutionary War: One thousand five hundred soldiers of the 6th Pennsylvania Regiment under General Anthony Wayne's command rebel against the Continental Army's winter camp in Morristown, New Jersey in the Pennsylvania Line Mutiny of 1781 |
| 25 | January 1 | Event | 1788 – First edition of The Times of London, previously The Daily Universal Register, is published. |
| 26 | January 1 | Event | 1800 – The Dutch East India Company is dissolved. |
| 27 | January 1 | Event | 1801 – The legislative union of Kingdom of Great Britain and Kingdom of Ireland is completed to form the United Kingdom of Great Britain and Ireland. |
| 28 | January 1 | Event | 1801 – The dwarf planet Ceres is discovered by Giuseppe Piazzi. |
| 29 | January 1 | Event | 1803 – Emperor Gia Long orders all bronze wares of the Tây Sơn dynasty to be collected and melted into nine cannons for the Royal Citadel in Huế, Vietnam. |
| 30 | January 1 | Event | 1804 – French rule ends in Haiti. Haiti becomes the first black republic and second independent country in North America after the United States |