(from the united nations official site)

It’s a day to be happy, of course! Happiness is a fundamental human goal. The United Nations General Assembly recognizes this goal and calls for “a more inclusive, equitable and balanced approach to economic growth that promotes the happiness and well-being of all peoples.” 

And GCDN, just like the United Nations, invites each person of any age, plus every classroom, business and government to join in celebration of the International Day of Happiness.