In the last thirty years, April 20 has become like a Saint Patrick’s for stoners: one glorious day to get completely blazed with other potheads worldwide. As such, the number 420 has also evolved into a ubiquitous symbol of canna-culture. Apartments are listed as “420-friendly,” clinics specify their “420 doctors” in neon, and in Denver, “420 tours” of dispensaries are a tourist’s must-do. While any self-respecting pothead may be able to rattle off several cryptic urban legends about the number’s mythical origins, the true story behind 420 is a more innocent tale of youth, high school, and friendship.

But first, the bullshit. Rumors have swirled in the air like clouds of dank smoke since the dark days before the internet. Here are some things that 420 is not:

420 is not the police code for marijuana violations, nor is it the California penal code for marijuana

This popular rumor is silly: why would weed smokers use a codeword that police themselves created? As for the California penal code, 420 refers to “obstructing entry on public land.” We suppose you’d want to obstruct entry to public land if you planted your pot crops on it, but that would be a rare circumstance.

420 is not the number of chemical compounds in weed

It would be pretty cool if a group of government scientists started referring to weed as “420” after discovering THC had 420 chemical compounds. Unfortunately, the cannabis molecule contains at least 483 chemical constituents. Sorry, nerds.

4/20 is not the death day of anybody in “The 27 Club”

The sentiment is nice, but 420 is not a tribute to any  “gone-too-soon” musicians. Jim Morrison died on July 3, Jimi Hendrix died on September 18, Janis Joplin on October 4, and Kurt Cobain on April 5.

4:20 is not “the best time” to plant marijuana

We’re not sure where this rumor grew its roots, since pot plant harvest season varies around the world. If you’re wondering, California farmers typically plant their seeds in mid-March, but drought conditions and winter frosts can change seeding schedules.

Now, for some bizarre coincidences….

4/20 is Adolph Hitler’s birthday

There certainly must be some neo-nazis and white supremacists who smoke pot, and 4/20 does happen to be the day Adolph Hitler was born, but there’s no evidence for a connection between marijuana and the Führer’s birthday.

4:20 is the time LSD scientist, Albert Hofmann first dropped acid

Notes from Albert Hofmann’s lab support the fact that the first deliberate acid trip by the discoverer of LSD occurred on April 19, 1943 at 4:20. Hofmann accidentally ingested lucy on April 16. Again, sorry nerds, there’s no relationship between marijuana and Hofmann’s experiments.

420 is the number you get when multiplying digits in a Bob Dylan song title

Ready for some far out nonsense? The Bob Dylan song, “Rainy Day Woman no. 12 and no. 35,” which contains the dope lyric, “Everybody must get stoned,” also apparently contains a math problem. When you multiply 12 and 35, the answer is 420. We’d love to know which strain caused some stoner of yore to figure this out, but unfortunately there’s no link between Dylan and 420.

The real story

As always, the truth is stranger (and somehow more adorable) than fiction. 420 all began in 1971 in San Rafael, California, with a group of high school students looking for an adventure. Known as “The Waldos,” because they liked to hang out by a wall (see? adorable), the teens came into possession of a hand-drawn map supposedly locating a long-lost marijuana plant. As legend had it, a member of the Coast Guard had abandoned the crop near Point Reyes. Like a spin-off episode of Stranger Things, The Waldos would meet every day at 4:20 in front of a statue of Louis Pasteur to smoke pot and search for the fabled crop.

The teens never did find the legendary crop, but they used “420” as a codeword to smoke pot so often that it became common slang to mean marijuana at their school. In a perfect coincidence, one of the Waldo’s older brothers mentioned the phrase to his friend, Phil Lesh, who happened to be the bassist for the iconic band, The Grateful Dead. Lesh, finding 420 to be totally groovy, shared the slang with his bandmates. It wasn’t long until the Dead began shouting out 420 at their concerts, using it on posters, and printing it on t-shirts.

But, while Deadheads made the connection between the number and that sticky icky, mainstream use of the term was relatively niche. It wasn’t until 1990 that Steve Bloom, a contributor to High Times, spotted an explanation of 420 on a Grateful Dead concert ad. Bloom loved the term and began using 420 to mean, well, 420, which helped to popularize the term worldwide.

So on this 4/20, when your friends start with tales of Jim Morrison’s day of death or more Bob Dylan theories, tell them to light up in respect for The Waldos instead. And let us know if you find any pot plants out near Point Reyes! Happy high holiday!

Follow Claire Downs on Twitter