Sign up for the Slatest to get the most insightful analysis, criticism, and advice out there, delivered to your inbox daily. Where, exactly, did National Bagel Day come from? Who decided that it must be held annually on Jan. 15? And how on earth am I supposed to celebrate? I have asked myself these questions far too many times over the years. As we’ve learned, perhaps against our will, the United States of America is home to zillions of bespoke microholidays recognizing the heritage of our great nation’s consumer products. Every morning on social media, the tributes come rolling in....