World War I – known at the time as “The Great War” – officially ended when the Treaty of Versailles was signed on June 28, 1919, in the Palace of Versailles outside the town of Versailles, France. However, fighting ceased seven months earlier when an armistice, or temporary cessation of hostilities, between the Allied nations and Germany went into effect on the eleventh hour of the eleventh day of the eleventh month. For that reason, November 11, 1918, is generally regarded as the end of “the war to end all wars.”
Veterans Day continues to be observed on November 11, regardless of what day of the week on which it falls. The restoration of the observance of Veterans Day to November 11 not only preserves the historical significance of the date, but helps focus attention on the important purpose of Veterans Day: A celebration to honor America’s veterans for their patriotism, love of country, and willingness to serve and sacrifice for the common good.
Sourced from https://department.va.gov/veterans-day/history-of-veterans-day