Invented in 2007 by a group of co-workers from the western Chicago Suburb of Wood Dale, IL, Mustache De Mayo is often abbreviated to "MDM". Mustache De Mayo is a celebration of May 5th by proudly displaying hair on your upper lip for just one day. To achieve the maximum unveiling of the mustache, a full beard or goatee must be grown in advance. Most often than not the MDM participant will create a persona and dress up in a fashion that suits the "stache".
Mike: Hey did you see Carl's molestache
Evan: Yup, It's Mustache De Mayo again!