Monday marks 4/20, the unofficial cannabis day

(CNN, KYMA) - Monday is April 20, or 4/20. To some people, it's a day to celebrate marijuana, but not many people know how 4/20 became associated with cannabis.

There are lots of stories out there, and the truth is no one knows for sure, but the term gained national attention when "High Times" magazine printed a flyer in 1991 that invited people to smoke on April 20 at 4:20 p.m.

The flyer originated with Grateful Dead fans in Oakland, California.

Here's where things get murky. The date and time allegedly originated with a roadie for the band named Dave Reddix.

He said when he was in high school in the 70s, he and some friends smoked marijuana at 4:20 p.m. after school.

Then, they started using 420 as code for smoking it.