Just a few minutes ago, I got around to Googling it and found the official National History Day website, where I found a wealth of information about National History Day. For example, I learned that it's "a highly regarded academic program for elementary and secondary school students" that "makes history come alive for America's youth by engaging them in the discovery of the historic, cultural and social experiences of the past." I learned it has been endorsed by many organizations, such as the American Association for State and Local History, the National Association of Secondary School Principals, and the Society of American Archivists. I learned that it had been awarded the 2011 National Humanities Medal by President Barack Obama. I learned that past themes of National History Day have included The Individual (1980), Conflict & Compromise (1986), Rights (1991), Migration (1998), and Innovation (2010), and that the 2014 theme is Rights and Responsibilities in History.
Here's what I didn't learn: the date. Doesn't that seem like a sensible thing for a National [subject] Day organization to put on its website? It seems that way to me. To test my theory, that I Googled "National Day" and visited several of the National [Subject] Day websites returned by that search. And guess what? Having visited those four websites, I now know the dates of National Day of Unplugging (sundown-to-sundown March 7-8), National Day of Civic Hacking (June 1-2), National Day of Reason (May 1), National Day of Listening (November 23), National Day of Prayer (first Thursday of May), and National Day on Writing (October 20). In every case but one, the date of the observance was right on the home page; I found the date of the one exception, National Day of Prayer, on the About page.
The National History Day website, on the other hand, lists no one date anywhere that I could find, other than the dates of the National History Day Contest, which will be held June 15-19, 2014, in College Park, Maryland. But I would call that a week, not a day. Maybe one of those days is THE day, but if so the website doesn't say which one. Weird! What's the point of having a National Day if you don't tell people when that day is?