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.
1919January 1919 January 1 The Czechoslovak Legions occupy much of the self-proclaimed "free city" of Pressburg (now Bratislava), enforcing its incorporation into the new republic of Czechoslovakia. HMY Iolaire sinks off the coast of the Hebrides; 201 people, mostly servicemen returning home to Lewis and Harris, are killed. January 2–22 – Russian Civil War: The Red Army's Caspian-Caucasian Front begins the Northern Caucasus Operation against the White Army, but fails to make progress.
1910January 1910 January 6 – Abé people in the French West Africa colony of Côte d'Ivoire rise against the colonial administration; the rebellion is brutally suppressed by the military. January 8 – By the Treaty of Punakha, the Himalayan kingdom of Bhutan becomes a protectorate of the British Empire. January 11 – Charcot Island is discovered by the Antarctic expedition led by French explorer Jean-Baptiste Charcot on the ship Pourquoi Pas? Charcot returns from his expedition on February 11.
1973January 1973 January 1 – The United Kingdom, the Republic of Ireland and Denmark enter the European Economic Community, which later becomes the European Union. January 15 – Vietnam War: Citing progress in peace negotiations, U.S. President Richard Nixon announces the suspension of offensive action in North Vietnam. January 17 – Ferdinand Marcos becomes President for Life of the Philippines. January 20 – Richard Nixon is sworn in for a second term as President of the United States.
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.
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.
1970January 1970 January 1 – Unix time epoch reached at 00:00:00 UTC. January 5 – The 7.1 Tonghai earthquake shakes Tonghai County, Yunnan province, China, with a maximum Mercalli intensity of X (Extreme). Between 10,000 and 14,621 are killed and 26,783 injured. January 14 – Biafra capitulates, ending the Nigerian Civil War. January 15 – After a 32-month fight for independence from Nigeria, Biafran forces under Philip Effiong formally surrender to General Yakubu Gowon.
19451945 marked the end of World War II and the fall of Nazi Germany and the Empire of Japan. It is also the year concentration camps were liberated and the only year in which atomic weapons have been used in combat. Below, the events of World War II have the "WWII" prefix. January 1945 January 1 – WWII: Germany begins Operation Bodenplatte, an attempt by the Luftwaffe to cripple Allied air forces in the Low Countries. Chenogne massacre: German prisoners are allegedly killed by American forces near the village of Chenogne, Belgium.
1916Below, the events of the First World War have the "WWI" prefix. January 1916 January 1 – The British Royal Army Medical Corps carries out the first successful blood transfusion, using blood that had been stored and cooled. January 9 – WWI: Gallipoli Campaign: The last British troops are evacuated from Gallipoli, as the Ottoman Empire prevails over a joint British and French operation to capture Constantinople. January 10 – WWI: Erzurum Offensive: Russia defeats the Ottoman Empire.
1978January 1 – Air India Flight 855, a Boeing 747 passenger jet, crashes off the coast of Bombay, killing 213. January 5 – Bülent Ecevit, of CHP, forms the new government of Turkey (42nd government). January 6 – The Holy Crown of Hungary (also known as Stephen of Hungary Crown) is returned to Hungary from the United States, where it was held since World War II. January 10 – Pedro Joaquín Chamorro Cardenal, a critic of the Nicaraguan government, is assassinated; riots erupt against Somoza's government.