On November 28th, 2012, Randall Munroe published an xkcd comic that was a calendar in which the size of each date was proportional to how often each date is referenced by its ordinal name (e.g. “October 14th”) in the Google Ngrams database since 2000. Most of the large days are pretty much what you would expect: July 4th, December 25th, the 1st of every month, the last day of most months, and of course a September 11th that shoves its neighbors into the margins. There are not many days that seem to be smaller than the typical size. February 29th is a tiny speck, for instance. But if you stare at the comic long enough, you may get the impression that the 11th of most months is unusually small. The title text of the comic concurs, reading “In months other than September, the 11th is mentioned substantially less often than any other date. It’s been that way since long before 9/11 and I have no idea why.” After digging into the raw data, I believe I have figured out why.