It seems there are two National Beer Days in the Unites States. The first was on April 7th which celebrates The first day beer sales became legal in the United States again after beginning of the end of Prohibition in the United States after President Franklin D. Roosevelt signed thet Cullen-Harrison Act into law.
September 28th is also National Beer day in the US but I find no source of its origin. Well since in our book every day is beer day and we have a lot to say about that. Beer Beer and More Beer.