1904January 1904 January 7 – The distress signal CQD is established, only to be replaced 2 years later by SOS. January 8 – The Blackstone Library is dedicated, marking the beginning of the Chicago Public Library system. January 12 – The Herero Wars in German South West Africa begin. January 17 – Anton Chekhov's last play, The Cherry Orchard («Вишнëвый сад», Vishnevyi sad), opens at the Moscow Art Theatre directed by Constantin Stanislavski, 6 month's before the author's death.
1888In Germany, 1888 is known as the Year of the Three Emperors. Currently, it is the year that, when written in Roman numerals, has the most digits (13). The next year that also has 13 digits is the year 2388. The record will be surpassed as late as 2888, which has 14 digits. January 3 – The 91-centimeter telescope at Lick Observatory in California is first used. January 12 – The Schoolhouse Blizzard hits Dakota Territory, the states of Montana, Minnesota, Nebraska, Kansas, and Texas, leaving 235 dead, many of them children on their way home from school.
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.
1894January 4 – A military alliance is established between the French Third Republic and the Russian Empire. January 7 – William Kennedy Dickson receives a patent for motion picture film in the United States. January 9 – New England Telephone and Telegraph installs the first battery-operated telephone switchboard, in Lexington, Massachusetts. February 12 French anarchist Émile Henry sets off a bomb in a Paris café, killing one person and wounding twenty.
1895January 5 – Dreyfus affair: French officer Alfred Dreyfus is stripped of his army rank, and sentenced to life imprisonment on Devil's Island. January 12 – The National Trust for Places of Historic Interest or Natural Beauty is founded in England by Octavia Hill, Robert Hunter and Canon Hardwicke Rawnsley. January 13 – First Italo-Ethiopian War: Battle of Coatit – Italian forces defeat the Ethiopians. January 17 – Félix Faure is elected President of the French Republic, after the resignation of Jean Casimir-Perier.
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.
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.
1905As the second year of the massive Russo-Japanese War begins, more than 100,000 die in the largest world battles of that era, and the war chaos leads to the 1905 Russian Revolution against Nicholas II of Russia (Shostakovich's 11th Symphony is subtitled The Year 1905 to commemorate this) and the start of Revolution in the Kingdom of Poland. Canada and the U.S. expand west, with the Alberta and Saskatchewan provinces and the founding of Las Vegas.
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.
1942The Uppsala Conflict Data Program project estimates this to be the deadliest year in human history in these terms of conflict deaths, placing the death toll at 4.62 million. However, the Correlates of War estimates that the prior year, 1941, was the deadliest such year. Death toll estimates for both 1941 and 1942 range from 2.28 to 7.71 million each. Below, the events of World War II have the "WWII" prefix.