Ah, April 20.

It's the one day where I can't tell who is more obnoxious: stoners who need everyone to know how much weed they plan to smoke or nonsmokers who need everyone to know that they have not and will never — emphasis on never — take a puff of a joint.

No matter where you fall on the spectrum, you're sure to get a whiff of ganja sometime throughout the day (especially as the clock strikes 4:20, when the stars align for weed enthusiasts who ritualistically light up). You're also sure to run into at least one red-eyed person today who has "allergies" — but we all know what's really going on there.

Entrepreneurs themselves are trying to make some green off the equally emerald substance. General Mills put up a billboard advertising Totino's Pizza Rolls in Denver that reads "420 is better on pizza rolls." Wiz Khalifa is set to drop his own line of marijuana products in pot shops throughout Colorado on Wednesday as well.

Basically, the holiday gets a little smellier and a little more profitable every year. But hidden in all the hoopla surrounding nearly every rapper's favorite drug is another important question: Why exactly has 420, both the date and the time of day, become associated with weed?

First it's important to dispel some pesky rumors that, while interesting, are proven to be false.

Some people say the number 420 is a reference to the number of chemical compounds in kush. That exact number is a little hazy, with some weed-centric outlets estimating 315 and other research journals putting the number at 483, so we can cross that one off the list.

Other people argue that 420 is the penal code for marijuana use in California. While that sounds like the perfect rebellious origin for weed, 420 is actually the penal code for obstructing entry to public property — nothing related to pot here, sadly. It's not the police radio code for ongoing marijuana smoking, either, as some claim.

The answer isn't that the Grateful Dead would always request to be in room 420 when staying in hotels, with band spokesman Dennis McNally refuting those claims. It's also not that Jimi Hendrix or Janis Joplin died on April 20, because they died in September and October, respectively.

So how exactly did April 20 become the St. Patrick's Day of weed?

The truth is stranger than any fiction you can imagine and maybe even more mind-blowing than today's celebrations. According to reports from multiple outlets, including The Huffington Post and High Times, it started in 1971 with a group of teenage potheads from San Rafael High School in California.

The group, who referred to themselves as "the Waldos," one day came across a map that detailed where a patch of cannabis was growing, just waiting to be rolled up and smoked. Classes would end at 3 p.m., but the group's members had sports practice until 4 p.m., so the enthusiastic weed heads would meet at their school's statue of Louis Pasteur at 4:20 and then head out in search of the elusive marijuana.

They never found the weed, but they made sure to bring plenty of their own during their adventures, as any good stoner would. Despite coming up short, the group soon started using '420' as a slang term to reference the substance they pined after.

"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, 'Do you have any?' Or, 'Are you stoned right now?' It was kind of telepathic just from the way you said it," said Steve, one of the Waldos, who asked for his full identity to be withheld when he spoke to The Huffington Post. "Our teachers didn't know what we were talking about. Our parents didn't know what we were talking about."

How it gained nationwide attention is even crazier. One member of the Waldos had a brother, referred to only as "Patrick" in The Huffington Post story, who said he was friends and often smoked marijuana with Phil Lesh, bassist and founding member of the Grateful Dead. Lesh, according to The Huffington Post, confirmed he was good buddies with Patrick and said he "wouldn't be surprised" if the Waldos came up with the term 420 and introduced it to him.

The use of the term grew faster than the line in Chipotle likely will today as it spread throughout the Dead fan base. High Times started to include references to '420' in its articles — even purchasing the domain name 420.com — and the term soon gained the mass attention it has today.

It's a crazy story, and one worth mulling over. So, if you plan to participate in today's festivities, spark up a joint, sit back and try to wrap your head around that one. Or just mindlessly watch Netflix and stuff your face with Taco Bell. That works, too.