World Hello Day is observed worldwide every November 21. It encourages participants to greet at least ten people with the simple word "Hello," promoting peace and strengthening social relations. The holiday was established in 1973 by Brian McCormack, a PhD graduate of Arizona State University, and Michael McCormack, a Harvard University graduate, in response to the Yom Kippur War between Israel and Egypt. The celebration aims to highlight the importance of communication over conflict resolution through force. By participating, individuals contribute to a global expression of peace and draw attention to the value of dialogue in resolving disputes.