History
The holiday developed during the 1980s as several chapters of the American Humanist Association (AHA) began to celebrate it. At the time, the date on which it was celebrated varied from chapter to chapter, with selections such as the founding date of the IHEU, or other significant dates. From the late 1980s to the early 1990s, the AHA and IHEU passed resolutions declaring World Humanist Day to be on June 21st, on or around the summer solstice.
http://en.wikipedia.org/wiki/World_Humanist_Day
Let's celebrate
