US law provides for the declaration of selected public observances by the President of the United States as designated by Congress or by the discretion of the President. Generally the president will provide a reasoning behind the elevation of the day, and call on the people of the United States to observe the day "with appropriate ceremonies and activities". These events are typically to honor or commorate a public issue or social cause, ethnic group, historic event or noted indivdual. However, (with several exceptions) there is no requirement that government or business close on these days, and many members of the general public may not be aware that such holidays even exist. Holidays proclaimed in this way may be considered a U.S. "national observance", but it would be improper to refer to them as a "Federal holiday".
In addition to annual commemorative events, the President may proclaim a day or period designated for mourning or prayer after the death of noted officials including US Presidents and Justices of the Supreme Court and after major tragic events or disasters with serious causalties.
^ Although not officially proclaimed by the President, it is typical for the President to issue a statement recogizing the events in Armenia and their aftermath.
^ Obeserved as Armistice Day from 1919-54. Between 1968-75, observed on fourth Monday of October.
^ Oldest proclaimed observance in US history, dating back to 1863 with Abraham Lincoln.