Today is Veterans Day in the U.S. Originally called Armistice Day, it was established to honor veterans of World War I but now honors all American veterans. Because the specific date, November 11, 1918 is considered the end of World War I, the holiday is celebrated on the actual day of the week upon which November 11th falls each year to preserve the historic significance of the date.
Here's a little more background on this holiday:
In November 1919, President Wilson proclaimed November 11 as the first commemoration of Armistice Day with the following words: "To us in America, the reflections of Armistice Day will be filled with solemn pride in the heroism of those who died in the country’s service and with gratitude for the victory, both because of the thing from which it has freed us and because of the opportunity it has given America to show her sympathy with peace and justice in the councils of the nations…" [History of Veterans Day, U.S. Department of Veterans Affairs.]
For Veterans Day resources including historical background, Presidental Proclamations, information on national and regional observances, a poster gallery, and more, visit the U.S. Department of Veterans Affairs, Veterans Day page.
Also check out: The Veterans History Project (Library of Congress).