From the official UN website:

"The International Day for the Elimination of Racial Discrimination is observed annually on 21 March. On that day, in 1960, police opened fire and killed 69 people at a peaceful demonstration in Sharpeville, South Africa, against the apartheid "pass laws". Proclaiming the Day in 1966, the General Assembly called on the international community to redouble its efforts to eliminate all forms of racial discrimination"