World Day for Cultural Diversity for Dialogue and Development is observed on May 21, 2017. The World Day for Cultural Diversity for Dialogue and Development is a United Nations-sanctioned international holiday for the promotion of diversity issues. Diversity Day is an opportunity to help communities understand the value of cultural diversity and learn how to live together in harmony. It was adopted in the wake of the terrorist attacks on September 11, 2001. The United Nations General Assembly proclaimed this holiday due to UNESCO's Universal Declaration on Cultural Diversity in November 2001. It was proclaimed by UN Resolution 57/249.
The many separate societies that emerged around the globe differed markedly from each other, and many of these differences persist to this day. As well as the more obvious cultural differences that exist between people, such as language, dress and traditions, there are also significant variations in the way societies organize themselves, in their shared conception of morality, and in the ways they interact with their environment. Cultural diversity can be seen as analogous to biodiversity. (With material from: Wikipedia)