World UFO Day is commemorated by some on June 24th, and others on July 2nd. The first, June 24, 1947 is generally considered to be the first widely reported UFO sighting in the United States by aviator Kenneth Arnold. July 2nd of that same year was the date of the supposed UFO crash in Roswell, New Mexico. July 2nd was declared the official World UFO Day by the World UFO Day Organization. It is believed that the first World UFO Day was celebrated in 2001 by UFO researcher Haktan Akdogan.

The stated goal of the July 2 celebration is to raise awareness of “the undoubted existence of UFOs” and to encourage governments to declassify their files on UFO sightings.