score:24
I would say the 1919 date references the signing of the treaty ending the war (emphasis mine) :
A formal state of war between the two sides persisted for another seven months, until the signing of the Treaty of Versailles with Germany on 28 June 1919.
Even though the actual fighting stopped in 1918:
On 11 November, at 5:00 am, an armistice with Germany was signed in a railroad carriage at Compiègne. At 11 am on 11 November 1918—"the eleventh hour of the eleventh day of the eleventh month"—a ceasefire came into effect.
This was, as noted a ceasefire, so the war did not 'officially' end until the signing of the Treaty of Versailles:
The Treaty of Versailles (French: Traité de Versailles) was the most important of the peace treaties that brought World War I to an end. The Treaty ended the state of war between Germany and the Allied Powers. It was signed on 28 June 1919, exactly five years after the assassination of Archduke Franz Ferdinand
Upvote:1
British troops continued to operate in north Russia through to early 1919 as an aftermath of the eastern front and Russian revolution. One of my ancestors died in February 1919 near Murmansk during these operations. Where local regiments were involved memorials often show the dates as 1914 to 1919.