Something similar seemed to happen recently during the NCAA tournament, when the St Peters Peacocks won a major upset over Purdue on March 25. News outlets from NBC to the WSJ all reported that March 25 was "National Peacock Day", and a Google search for "When is national peacock day" seems to confirm this with a knowledge panel.

If you dig deeper though, there actually appears to be no such day, and the first reference to it other than a Draft Kings blog post was a Peacock Day event being held at the LA Arboretum years back.

Obviously such a trivial story has no real impact on the world, but it was eye-opening to see how a "fact" could essentially be brought to life out of nowhere.