This past March, the latter of the aforementioned books along with five others (featured in an uncredited web-image below) were pulled from any re-publication in the future, due to accusations that they contain racist's undertones.
But getting back to the date of May 15th, acccording to multiple sources, it was also the day that Seuss was elected as editor-in-chief of the Dartmouth school newspaper, The Jack-O'-Lantern.
As for me and May 15th, I have referenced it's connection with Horton hearing a who while being in the Jungle of Nool in a number of posts within this blog.

