According to Humanists International, the day is a way of spreading awareness of Humanism as a philosophical life stance and means to effect change in the world.
The holiday developed during the 1980s as several chapters of the American Humanist Association (AHA) began to celebrate it.
From the late 1980s to the early 1990s, the AHA and IHEU passed resolutions declaring World Humanist Day to be on the northern summer solstice.
Whilst the event might be a simple gathering, such as a dinner or picnic, with ample time for both socialising and reflection, the method of celebration is down to the individual Humanists.
Some groups actually develop intricate social rituals, music, and proceedings which highlight the metaphoric symbolism of the solstice and the light (knowledge) which brings us out of darkness (ignorance).