Such days include those marking the death or funeral of a renowned individual or individuals from a country of that organization or elsewhere or the anniversary of such a death or deaths, the anniversaries of a significant natural or man-made disaster occurring in the country of the organization, wartime commemorations or in memory of the victims of a terrorist attack.
Common symbols include flying the organization's flag at half-mast and observing minutes of silence.
The concept was first introduced by European Commission in September 2001 after the terrorist attacks in the United States.
[1][2] The Arab League observed three days of mourning for the death of King Fahd of Saudi Arabia on 4 August 2005.
[3] After these, many organizations observed day of international mourning for several times.