1920January 1920 January 1 Polish–Soviet War in 1920: The Russian Red Army increases its troops along the Polish border from 4 divisions to 20. Kauniainen, completely surrounded by the city of Espoo, secedes from Espoo as its own market town. January 3 – The 1920 Xalapa earthquake in Mexico kills over 600 people, making it the second deadliest in the country. January 7 – Russian Civil War: The forces of Russian White Admiral Alexander Kolchak surrender in Krasnoyarsk; the Great Siberian Ice March ensues.
1899January 1 Spanish rule ends in Cuba, concluding 400 years of the Spanish Empire in the Americas. Queens and Staten Island become administratively part of New York City. January 2 Bolivia sets up a customs office in Puerto Alonso, leading to the Brazilian settlers there to declare the Republic of Acre in a revolt against Bolivian authorities. The first part of the Jakarta Kota–Anyer Kidul railway on the island of Java is opened between Batavia Zuid (Jakarta Kota) and Tangerang.
1976January 1976 January 2 – The International Covenant on Economic, Social and Cultural Rights enters into force. January 5 – The Pol Pot regime proclaims a new constitution for Democratic Kampuchea. January 18 – Full diplomatic relations are established between Bangladesh and Pakistan 5 years after the Bangladesh Liberation War. January 27 The United States vetoes a United Nations resolution that calls for an independent Palestinian state. The First Battle of Amgala breaks out between Morocco and Algeria in the Spanish Sahara.
1972Within the context of Coordinated Universal Time (UTC) it was the longest year ever, as two leap seconds were added during this 366-day year, an event which has not since been repeated. (If its start and end are defined using mean solar time [the legal time scale], its duration was 31622401.141 seconds of Terrestrial Time (or Ephemeris Time), which is slightly shorter than 1908). January 1972 January 1 – Kurt Waldheim becomes Secretary-General of the United Nations.
1913January 1913 January 3 – First Balkan War: Greece completes its capture of the eastern Aegean island of Chios, as the last Ottoman forces on the island surrender. January 13 – Edward Carson founds the (first) Ulster Volunteer Force, by unifying several existing loyalist militias to resist home rule for Ireland. January 18 – First Balkan War: Battle of Lemnos – Greek admiral Pavlos Kountouriotis forces the Turkish fleet to retreat to its base within the Dardanelles, from which it will not venture for the rest of the war.
1915Below, the events of World War I have the "WWI" prefix. January 1915 January – British physicist Sir Joseph Larmor publishes his observations on "The Influence of Local Atmospheric Cooling on Astronomical Refraction". January 1 WWI: British Royal Navy battleship HMS Formidable is sunk off Lyme Regis, Dorset, England, by an Imperial German Navy U-boat, with the loss of 547 crew. Battle of Broken Hill: A train ambush near Broken Hill, Australia, is carried out by two men (claiming to be in support of the Ottoman Empire) who are killed, together with four civilians.