1337 day is the 13th of March, 2007 (13/3/7). Unfortunately, not available to American counterparts due to their switching of the month and the day. 1337 Day will be celebrated by hax0rs alike around the world.
Student1: Yo, what youz doing on leet day?
Teacher: What is leet day?
Student2: Its teh fo shizzle j00 nub!!!!111
Teacher: Oh, you mean 1337 day. Whos teh nub now? i hax your mum.
Man I am so leet.
Maybe so, but I'm a 1337 hax0r, and its my bday in teh 07!