Happiness, true happiness, is an inner quality. It is a state of mind. If your mind is at peace, you are happy. If your mind is at peace, but you have nothing else, you can be happy. If you have everything the world can give - pleasure, possessions, power - but lack peace of mind, you can never be happy.
By designating a special day for happiness, the UN aims to focus world attention on the idea that economic growth must be inclusive, equitable, and balanced, such that it promotes sustainable development, and alleviates poverty. Additionally the UN acknowledges that in order to attain global happiness, economic development must be accompanied by a balance of social and environmental well-being.