(noun): Traditionally occurs the first day of June. First celebrated in 1981, but not recognized as a populist South American holiday until 1999. Although it is derided by some as just another effort to promote a cult of personality, most accept its significance as a Day of National Forgetfulness and Drinking.
Example 1: Holy wowsers, it's Trey Day... where the shit are the kegs?
"It's Trey Day, baby!" - B. Plance