The "official time" to smoke it up...
The original story:
A small group of kids in high school used to meet up everyday after school at 4:20 and smoke on the hill. One day on April 20th, at 4:20 they were all like "woa...it's 4:20, and 4/20- we should make this celebration official" the celebration spread and now 4/20 is an amazing day to get blazed thanks to a group of high school kids from norcal from the 70's