Global cannabis suppliers struggled to keep up with demand on Saturday, the biggest ever 4/20 Day, an annual celebration of marijuana on 20 April, which in the US calendar is referred to as 4/20.

Suppliers in the US, where recreational cannabis is legal in 10 states, and Canada, where the drug was decriminalised for recreational use last year, reported difficulties fulfilling orders on what has been called the industry’s Black Friday.

Some delivery websites, and the biggest legal delivery app, Eaze, crashed under the weight of demand on Saturday. Online cannabis dispensaries Nugg and Chill also suffered difficulties throughout the day.

Eaze crashed repeatedly soon after it began “happy hour”, with free delivery in California, and a 20% discount on cannabis-related products in other states.

✨It’s Happy Hour. ✨



Free delivery. 🥳

9am - 2pm PST. — Eaze (@eaze) April 20, 2019

“We know Eaze.com is experiencing intermittent outages and have all hands on deck working to keep up with demand,” the company said on Twitter. “Thank you for your patience.”

“The volume was unprecedented - cannabis has definitely gone mainstream,” an Eaze spokeswoman said. “The lines to dispensaries across California were out the door.”

A spokesperson for the Canadian government said: “Health Canada is aware of reports of localised shortages of cannabis products in some markets and for some product lines.”

Armen Yemenidjian, the chief executive of Essence Cannabis Dispensaries, which is based in Las Vegas, said 20 April was “definitely the Black Friday of the industry”, in reference to the day in November that has become the busiest shopping day of the year.

“It also pays homage to the culture that has moved the cannabis industry forward for the past couple of decades,” he said in an interview with the Las Vegas Sun. “4/20 has been adopted by the mainstream and used as a symbol for cannabis.”

The annual celebration, which dates to the 1990s, has been hijacked by big brands seeking to cash in. Pizza Hut, Ben & Jerry’s ice-cream and the ride-sharing company Lyft this year all ran weed-themed promotions.

Pizza Hut cut the price of its Hershey triple chocolate brownie from $5.99 to $4.20 to coincide with weed day. Lyft offered rides in Massachusetts for $4.20, saying it did not want people to risk driving under the influence.

Ben & Jerry’s partnered with a San Francisco cannabis supplier to give all customers a free tub of its Half Bakedflavour, a combination of cookie dough and fudge brownie. The Vermont-based ice-cream maker is also calling on consumers to pressure lawmakers to expunge prior marijuana convictions for anyone arrested for smoking pot.

There were organised weed celebrations in Denver, San Francisco, Washington DC, New York, and in Hyde Park in central London. As the seconds ticked down to 4.20pm, thousands of people lit cannabis joints, and called on the government to decriminalise the class B drug.

Arcview, a cannabis investment and market research firm, estimates US retail sales of cannabis products jumped to $10.5bn (£8bn) last year, a threefold increase from 2017. Kit Yarrow, a consumer psychologist at Golden Gate University, said: “It’s still a celebration of marijuana but the conversation has been expanded by brands that tie into the cannabis industry and for marketers to tie into something that has a coolness to it.”

The origins of 4/20 day are unclear, but began with a group of friends in California in the 1970s who would meet up after school at 4.20pm to smoke weed.

The teenagers at San Rafael High school, about 20 miles north of San Francisco, would apparently arrange smoking sessions with the code “420 Louis”, which meant meet at 4.20pm near the school’s statue of Louis Pasteur.

“Back then, we spent every day of our lives worrying about getting busted,” Steve Capper, one of the members of the group, told the San Francisco Chronicle. “Going to buy was a really secret thing.” . While it started as an inside joke, 4/20 has stuck among weed users in the US and beyond.