World Down Syndrome Day (International)

World Down Syndrome Day (WDSD) is marked each year on March 21, beginning in 2007. The 21st day of March was selected to signify the uniqueness of the triplication (trisomy) of the 21st chromosome which causes Down syndrome. The General Assembly of the United Nations has decided to observe it each year since 2012.

Lists of holidays by various categorizations.

March 21 is the 80th day of the year in the Gregorian calendar; 285 days remain until the end of the year.