How 4/20 Became 'National Weed Day' It all started as a high school in-joke in 1971 By Ruth Brown, Newser Staff Posted Apr 20, 2013 3:02 PM CDT 34 comments Comments A women wears glasses with the likeness of marijuana leaves during the annual marijuana 420 smoke off at Dundas Square in Toronto on Friday, April 20, 2012. (AP Photo/The Canadian Press, Nathan Denette) (Newser) – It's April 20, the day on which marijuana enthusiasts around the country celebrate their favorite smokable green herb at events like the Cannabis Cup in Denver and Snoop Lion's (nee-Dogg's) 420 Festival in LA. But why April 20? The tradition can be traced back to a group of high school students in San Rafael, California, in 1971, reports the Huffington Post. The teens, who called themselves "the Waldos," would meet at 4:20pm after school and go in search of a rumored nearby marijuana plantation. They never found it, but "420" became their codeword for all weed-based discussion. "I could say to one of my friends, I'd go, '420,' and it was telepathic. He would know if I was saying, 'Hey, do you wanna go smoke some?' ... Or, 'Are you stoned right now?'" says one of the Waldos. The term began to catch on—thanks in no small part to the teens' social ties to the Grateful Dead. Traveling Deadheads spread "420" across the country, High Times magazine began organizing events around the number, and the rest is slightly hazy history.