Both marijuana smokers and non-smokers recognize April 20 or 4/20 as a national holiday for cannabis culture, but few actually know how the date got chosen.
In 1971, five students at San Rafael High School would reportedly meet at 4:20 p.m. by the campus's statue of chemist Louis Pasteur to partake. Two of these students, David Reddix and Steve Capper, wrote an article for The Huffington Post about how this group—known as the "Waldos" because they met at a wall—would say "420" to each other as code for marijuana.
A brother of a group member apparently knew Grateful Dead bassist Phil Lesh, so the band is said to have helped popularize the term. On Dec. 28, 1990, Deadheads in Oakland handed out flyers reportedly inviting people to smoke "420" on April 20 at 4:20 p.m—and one got in the hands of Steve Bloom, a former reporter for High Times magazine, an authority on cannabis culture. Once the publication published the flyer in 1991 and continued to reference the number, it became known globally for its association with marijuana. In 1998, the outlet recognized the "Waldos" as the "inventors" of 420 after they came forward.
Bloom, now the publisher of Celebstoner.com, has credited the people who wrote the flyer for the date's reputation as an annual gathering of pot smokers. "They wanted people all over the world to get together on one day each year and collectively smoke pot at the same time," he wrote last year. "They birthed the idea of a stoner holiday, which April 20 has become."
Source: Waxman, Olivia B. "Here's the Real Reason We Associate 420 With Weed." Time. Time, 19 Apr. 2016. Web. 05 Feb. 2017.