World Laughter Day takes place on the first Sunday of May of every year .[1] The first celebration was on January 10, 1998, in Mumbai, India, and was arranged by Dr. Madan Kataria, founder of the worldwide Laughter Yoga movement.
Laughter Yoga says: Laughter is a positive and powerful emotion that has all the ingredients required for individuals to master themselves and to change the world in a tubular way. The day is now celebrated worldwide.
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All details taken directly from provider content at http://en.wikipedia.org/wiki/World_Laughter_Day