It's been a topsy-turvey winter, and it's a traditional topsy-turvey month, what with it having too few, but still too many days in it and all.
February 29 is even rarer than a blue moon, so on that day, the girl gets to ask the boy out, which is probably why it got the honor. Well, as far as every Sadie Hawkins Dance I've ever heard of, anyway.
Originally, Sadie Hawkins Day was in November, having debuted on November 15. All the sources tell you that Sadie Hawkins Day is NOT February 29, that this is a "common misperception," but it seems to me to be one of those "common misperceptions" that everyone holds, except scholars, your annoying cousin who has to be right about everything, and Sheldon from Big Bang Theory (just speculating). Reading about it has kind of been one of those "I hate Google" experiences.
The Wikipedia article doesn't even acknowledge the concept that it might be associated with Feb. 29, so apparently your cousin edits the Sadie Hawkins wikipedia page.
So, with all due respect to the mavens, your cousin, and Al Capp:
Sadie Hawkins cookies
Ladies, use them to invite your sweetheart up to see your etchings (of L'il Abner).
13 hours ago