Today is also 4/20 or as those who are recreation users of the illegal substance marijuana refer to it simply as 420 (pronounced “four-twenty”).
The reference dates back to a group of high school kids at San Rafael High School in California back in 1971. They planned to meet to light up, 4:20 p.m. This wasn’t meant for a global call to all smokers, just a code they used. Needless to say it now one of the most common terms to refer to marijuana.
While I do not in anyway approve the use of said substance (where it is illegal), I do find it interesting to know the backstory of popular cultural references.