Guacamole, close up of the traditional Central American spread food. 'Guac' is an avocado-based dip, or salad first developed by the Aztecs in what is now Mexico. (Photo by Roberto Machado Noa/LightRocket via Getty Images) Bet you didn’t know there were two holidays dedicated to celebrating avocados.Much like National Avocado Day, which is held July 31, (and probably even Cinco de Mayo), National Guacamole Day, Sept.