To most people under the age of 30, 4/20 is recognized as the symbol for the date and time of cannabis consumption.

Celebrated around the world on April 20 with festivals, concerts and mass gatherings, this day-long toke-out is devoted to smoking copious amounts of marijuana, while immersing oneself in all things, well, marijuana.

But the legend, which has sparked blunts, bongs and dab rigs for more than 45 years, has evolved from a cult following to a cultural phenomenon.

The term 4/20 originated across the Richmond-San Rafael Bridge in San Rafael, circa 1971, by five San Rafael High School students dubbed the “Waldos.”

Upon hearing about a lost crop of marijuana in Point Reyes, the free-loving group of pot enthusiasts decided to go out in search of the stash.

Before each adventure, the Waldos agreed to meet up at 4:20 p.m. at the statue of French biologist Louis Pasteur to smoke a few joints.

After weeks of failed attempts to locate the treasured buds, the Waldos gave up the hunt, but continued their 4:20 rendezvous.

For the Waldos, the term became more of a code, a way to discretely reference smoking pot without anyone understanding exactly what they were doing.

The exclusive nature in which the term was used almost suppressed its emergence.

But it was Phil Lesh, bassist for the psychedelic rock band The Grateful Dead, who launched 4/20 into national spotlight.

Lesh, who was friends with members of the Waldos, also indulged heavily in pot smoking.

Lesh and the Grateful Dead soon adopted the term, incorporating it into their concerts as they traveled the country.

In 1991, while the Dead played a show in Oakland, fliers swirled through the crowd inviting attendees to smoke pot on April 20 at 4:20 p.m. on Mt. Tamalpais in Marin County.

So materialized the first mass 4/20 gathering where people celebrated and smoked marijuana.

It was the Grateful Dead who popularized the connection between 4/20 and marijuana, while advocating the consumption of cannabis at 4:20 and on April 20.

Throughout the years, April 20 has become known as “Marijuana Day,” a holiday with celebrations across the United States.

San Francisco’s Hippie Hill, located in Golden Gate Park, is home to one of the nation’s biggest 4/20 celebrations, with crowds and clouds nearing 10,000 in 2016.

In Tallahassee, Florida, attendees clad in tie-dye shirts, flip-flops and overfilled hash pipes made 2016 the largest 4/20 crowd on record with over 20,000.

Other notable events take place in states including Colorado, Oregon, New York and Illinois, as well as in Canada, where some of the biggest gatherings and festivals are held.

And 4/20 has even made its way into mainstream popular culture, presenting itself in movies, music and on television.

It has become so present in society that there’s even a Snapchat filter for the actual day.

And the observance of 4/20 does not seem to be slowing down.

In fact, it’s only getting bigger. As people from all walks of life get involved in 4/20 celebrations with a puff or two, opposition turns into acceptance.

And this acceptance is growing, as more states legalize the recreational use of marijuana.