Sunday is Veterans Day. This annual event often gets overlooked on the calendar in the run-up to Thanksgiving and the December holidays. But this Veterans Day is special. It’s the 100th anniversary of the unofficial end of World War I.

The actual peace treaty wasn’t signed until later, but November 11, 1918 — at the 11th hour of the 11th day of the 11th month — is when a truce called an armistice (pronounced ARM-iss-tiss) was signed and the fighting stopped.

One year later, President Woodrow Wilson declared November 11 Armistice Day. Other countries did the same, some calling it Remembrance Day. In this country, Armistice Day was renamed Veterans Day in 1954.

World War I was one of history’s largest wars. Most of the fighting was in Europe, but 30-plus countries took part, including the United States. More than 29 million soldiers worldwide died or were wounded, and an estimated 13 million civilians died — a horrific toll that led to it being branded “the war to end all wars.”

A poster for all

Each year, a U.S. competition is held to design a poster for Veterans Day. The winning entry appears on pins and on the cover of the program for a ceremony at Arlington National Cemetery.

This year’s theme, “The War to End All Wars,” drew about 80 entries. Adam Grimm, whose design won, kept it simple. His poster has a large red poppy, the worldwide symbol for remembering World War I (see box); barbed wire to show the brutality of the war; and the pink hue of a rising or setting sun, showing the passage of time.

Two holidays of honor

Many Americans confuse Veterans Day with Memorial Day, another U.S. holiday related to the military.

Memorial Day began as Decoration Day in the 1860s following the Civil War. After World War I, its meaning changed. It honors U.S. military who died in any conflict, and it is observed on the last Monday in May.

Veterans Day also reflects a new meaning from the original Armistice Day, which honored all who served in World War I, but especially those who died. By 1954, the United States had fought in World War II and the Korean War. Lawmakers decided to rename the day to honor all American military, past and present, whether they served in war or peace.

In the 1970s, Veterans Day was observed on the fourth Monday in October so workers could have a three-day weekend. But it was an unpopular change. Many people liked the holiday’s connection to the armistice signing. So, since 1978, U.S. veterans have been officially honored on November 11.

The poppies of Flanders

In Flanders fields the poppies blow

Between the crosses, row on row . . .

In 1915, a Canadian doctor and soldier, mourning a friend’s death in battle in the Flanders region of Belgium, wrote a poem noting how quickly poppies grew around the soldiers’ graves. The bright red wildflowers were a sign of life in a bleak landscape.

The poem “In Flanders Fields” (the opening lines are printed above) became very popular, and the red poppy became a sign of remembrance. People started wearing silk poppies to honor the war dead. To mark the 100th anniversary of the start of the war, 888,000 ceramic poppies filled the moat at the Tower of London in 2014.

Arlington remembers

Arlington National Cemetery hosts a free public ceremony every Veterans Day. It starts at 11 a.m. with a wreath-laying at the Tomb of the Unknowns. Shuttle buses begin running at 8 a.m.

Three unidentified Americans from different wars are buried at the site. A large marble box rests atop the grave of the World War I Unknown. There used to be four graves, but because of advances in medicine and science, the Vietnam Unknown was identified in 1998 and reburied elsewhere.