For those in the marijuana culture, “4/20” is the highest holiday.

For close to 40 years, April 20  -- the 20th day of the fourth month-- has been the day to celebrate all things marijuana and to call for loosening of what many say are outdated laws that ban the substance. But the origins of the day have been as hazy as the clouds of smoke that waft from the hundreds who gather in public spaces to celebrate it. Here’s a look at how “Weed Day” began and where it’s headed now.

Why 4/20?

Though “420” is often used in pot parlance, few are sure how the term became rooted in popular culture. It’s fairly certain that the word began in California and spread from there, but why remains a mystery.

Some claimed it refers to sections of the California penal code banning the use of marijuana, but in fact, Section 420 actually deals with the legal right to enter public buildings or lands.

Others theorized it refers to a police radio code, but the Los Angeles Police doesn’t have a code 420 and, while the San Francisco Police do, their 420 code refers to a "juvenile disturbance."

The now widely accepted origin story traces back to a group of high school students, believe it or not.

The group’s members were buddies from San Rafael High School in northern California who called themselves "the Waldos," a nod to the term comedian Buddy Hackett used to describe odd people.

During the fall of 1971, the group began meeting after class, at exactly 4:20 p.m., to smoke a joint, and then head out to look for a legendary marijuana crop in the hills they had heard about.

The Waldos never did find the patch, but their private use of the term "420" somehow took on a life of its own. These days, it’s simply become shorthand for pot itself.

Why does Canada still celebrate 4/20?

For years, thousands of pot enthusiasts have gathered on Ottawa’s Parliament Hill, and in front of legislative buildings and art galleries in Toronto, Vancouver and other cities, to call for change to the provisions of the Controlled Drugs and Substances Act and other legislation that ban cannabis use. It all culminates with a synchronized smoke at 4:20 p.m.

But with recreational pot use about to become legal in just a few months, is there still any need? Pot activists say there is still plenty to fight for.

Many want to ensure there’s a “mixed retail” model, so that private merchants can sell cannabis alongside government entities, such as Ontario’s LCBO stores. Others want the right to open cannabis lounges.

And still others want to pot use in public spaces made legal, as well as special events permits similar to the temporary alcohol licences that are granted for summer outdoor events.

Why does the U.S. still celebrate 4/20?

Though pot is now legal in eight states, activists in the U.S. say there is still much work that needs to be done. Nothing has changed with federal laws, where marijuana is still a “Schedule 1” drug. That’s the same category as heroin, a category for drugs "with no currently accepted medical use and a high potential for abuse.”

U.S. pot activists also say they worry that the White House under U.S. President Donald Trump is still hostile toward legal marijuana.

But it’s true that in some areas where recreational marijuana use is now legal, 4/20 events are not what they used to be. In Colorado, celebrations have dropped off significantly in the six years since the state legalized the drug’s use.