The date for this special day was chosen because it is the date of the Roswell Incident, a historical event leading to wide speculation and belief that aliens have indeed visited us.
Organizers are downright serious about getting the overall public to believe that we indeed have been visited by aliens from outer space. They are seeking to get the U.S. and other governments to admit to what they believe is a reality.
Have we been visited by extra-terrestrial beings? You make the call.