WASHINGTON (CNN) -- Soldiers of the United States Army's 3rd Infantry Regiment stand guard at the Tomb of the Unknown Soldier at Arlington National Cemetary 24/7, regardless of inclement weather.
The Tomb of the Unknown Soldier (Tomb) was established in 1921. According to the Tomb's website, "The Unknown Soldiers laid to rest at the Tomb represent all missing and unknown service members who made the ultimate sacrifice - they not only gave their lives, but also their identities to protect these freedoms."
According to ArlingtonCemetary.mil, the guard is changed every hour on the hour Oct. 1 to March 31, and from April 1 through Sept. 30, another change is added on the half-hour.
Read all about the ritual: http://www.arlingtoncemetery.mil/visitorinformation/ChangingofTheGuard.aspx
Learn more about the Tomb of the Unknown Soldier