1914

Although the war essentially started on June 28, after the assassination of Archduke Ferdinand, Britain did not officially declare war on the German Empire until August 4, 1914. The next day, that announcement appeared in print.

"After more than four years of bloodshed, the Great War ended on November 11, 1918, after Germany, the last of the Central Powers, surrendered to the Allies. At the peace conference in Paris in 1919, Allied leaders would state their desire to build a post-war world that was safe from future wars of such enormous scale. The Versailles Treaty, signed on June 28, 1919, tragically failed to achieve this objective. U.S. President Woodrow Wilson’s grand dreams of an international peace-keeping organization faltered when put into practice as the League of Nations. Even worse, the harsh terms imposed on Germany, the war’s biggest loser, led to widespread resentment of the treaty and its authors in that country–a resentment that would culminate in the outbreak of the Second World War two decades later."

Source:

https://www.history.com/this-day-in-history/archduke-ferdinand-assassinated

Stefan Zweig (1941) mentions in his memoirs the feeling that spread out at the beginning of that year: "Europe was never stronger, richer and more beautiful. […] During 1900 until 1910 there was more freedom, carefreeness and ease than during the 100 previous years". 1914 is clearly known as the year that the First World War started, but it was not the only relevant social event that happened:

The English suffragism and the Mary Richardson attempt’s against The Venus of the Mirror (Velazquez's painting) in the National Gallery trying to stand her voice out because of her fellow believer Mrs. Pankhurst’s imprisonment, the murder of the French Socialist leader Jean Jaurès shot by the nationalist Raoul Villain in a restaurant because of his pacifist posture against the War, the establishment of the 8-hour work day in the Motor Ford Company and the minimum wage of 5€-equivalent per day, the use of radiation therapy for the first time in London, the inauguration of the Panama Canal which meant save 15,000 km for the ships, the beginning of the USA of a long process of adaptation as a superpower with the occupation of Veracruz, the publication of the first edition of the lyrical narrative Platero and I by the Spanish poet Juan Ramón Jiménez which, years later, it would become the third most translated work after The Bible and Don Quixote…

Following Antonio López (2014), “1914 would be known in History as the year in which a warlike conflict of dimensions hitherto unknown began, which would be etched with blood and fire in the conscience of the World. However, 1914 was much more than a war; it was the year that changed History”.

Sources:

López, A. (2014). 1914. El año que cambió la historia. España: Taurus

Zweig, S. (1964). The world of yesterday: An autobiography. Lincoln, Neb: University of Nebraska Press.