Here’s Why Marijuana Is Called 4:20
Steven Hager, a marijuana activist, promoter, journalist, filmmaker and editor of fan magazine "High Times" insists he knows the real origin of the phrase 4:20.
Ask any stoner and they'll tell you it was the police code for the crime of possessing marijuana... or that it's the time Mexican fieldworkers got done with their day and were allowed to relax.
But Hager insists those are all wrong. He says the phrase was made popular by Grateful Dead fans (Deadheads) from San Rafael, California.
Apparently in 1971 a group of students at San Rafael High School made a pact to search for, and share the whereabouts, of an abandoned cannabis field. The students would meet up at 4:20 (long after school ended) to go search for the hills. Pretty soon the whole school would refer to the use of cannabis as "4:20" and the term stuck. As Deadheads toured the country they spread the slang term.