World Smile Day® was created by Harvey Ball, who claimed to have designed the  Smiley Face® in 1963.
He designed his specific smiley as a design for buttons that would radiate a positive morale to whomever saw them.
These smiley buttons became one of the most popular designs for buttons for all decades to come.

In reality though, smiley faces are almost as old as human art.
The first documented and preserved smiley face was made by Bernard Hennet on 19 May 1741.

Harvey was concerned about commercialization of his particular Smiley Face®, so he created World Smile Day® to be celebrated from 1999 on. 

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The Harvey Ball World Smile Foundation was created to continue World Smile Day® after Harvey died in 2001.

Ironically enough, Harvey Ball did grab a lot of the credit for drawing the smiley face.
But he never earned a lot from it’s popularity because he never trademarked his design, so copycats all over the world ran with the happy face….and got the loot!

Sources:

• https://www.worldsmileday.com/
• https://www.worldsmile.org/