At 4:20pm, thousands around the world will participate in a synchronized smoke-off.

A cloud of smoke is wafting across cities worldwide today with the celebration of 4/20 – the unofficial holiday of marijuana – culminating in a synchronized smoke at 4:20pm.

Held on April 20 annually, the digits 4/20 have become synonymous with cannabis culture, as the date is written in the North American calendar as 4/20.

In Canada, it’s the end of an era in some ways, as this will be the last celebration before marijuana is set to become legal. Last year, an estimated 40,000 people attended Vancouver’s 4/20 celebration, with even more expected this year.

Why did 4/20 become synonymous with marijuana?

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of the fourth month-- has been the day to celebrate all things marijuana and to call for loosening of what many say are outdated laws that ban the substance.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.

'What this ruling really is, is a missed opportunity to liberalize trade,' Calgary economist says

A Supreme Court of Canada ruling on interprovincial beer imports has sparked fears that provinces and territories will be free to impose restrictions on cannabis flowing over their borders at a time the industry is in its early stages of growth.

In its ruling on the so-called free-the-beer case, the top court said provinces and territories can restrict imports of goods, as long as their intent isn't to impede trade.

Despite that proviso, economists said there is enough wiggle room in the decision allowing provinces to impose restrictions on the legal trade of cannabis.

It has at least one local pot company worried.

Less fish, more 4/20 if one local entrepreneur has his way

Cannabis could be coming to the rescue of a Newfoundland fishing community that's been without an economic centre since Hurricane Igor laid waste to the area in 2010. 

Port Union's old Ocean Choice International fish plant could soon be used to plant marijuana. 

The disused building is in the final stages of a sale to local businessman Daniel Porter, who is planning to turn it into a cannabis growing facility for medicinal and recreational pot.

"This means the world to me," Porter said.

"I love that I can come home and create work and have an impact on the community … it affects people's lives and children's lives, and it creates a massive employment spinoff."

City official predicts 'huge demand in Canada for that training'

Summerside, P.E.I., is hoping to get more officers trained as soon as possible to recognize drug-impaired drivers in advance of Canada's planned legalization of recreational marijuana.

Deputy chief administrative officer Gordon MacFarlane told CBC News only a handful of city officers are trained and the only available training is in Florida.

"Hopefully ... there will be something that will be able to be done through the Atlantic Police Academy because … no doubt there's going to be a huge demand in Canada for that training," he said.

Cannabis activists say although this year’s 4-20 celebrations across the country will likely be the last before recreational pot use becomes legal, there’s still a lot to fight for.

The federal government has committed to making marijuana legal by the summer, but the task of regulating the sale and consumption of the drug has been handed down to the provinces and territories.

Lisa Campbell with the Ontario Cannabis Consumer and Retail Alliance said she doesn’t think 4-20 events across the country will disappear with the new legalized system — but they will likely evolve.

A cloud of cannabis smoke will envelop Parliament Hill Friday during what will be, by all accounts, the last 420 celebration before recreational cannabis is legalized.

But there's also uncertainty hanging in the air — particularly when it comes to the question of where pot smokers will be able to light up in Ottawa. 

When the Ontario government passed its Cannabis Act, the province made it clear that smoking will not be allowed in any public places. It's even laid out the fines: $1,000 for a first offence and up to $5,000 when scofflaws are caught again. 

But in Ottawa, there's a wrinkle.

In the National Capital Region, where municipal, provincial and federal jurisdictions intersect, the regulations are more obscure.

U.S. dispensaries have strict advertising rules as they target 'canna-curious' people

Even before recreational marijuana is legal in Canada and the rules around advertising are fully developed, a licensed pot producer in Leamington, Ont. is targeting your senses with six 'cannabis experiences.'

In the days leading up to today's 4/20 pot celebrations, which will likely be the last before the planned cannabis legalization by the summer, Aphria introduced a new marijuana brand. It's called Solei Sungrown Cannabis and will be designed for the new adult-use market.

A day that's come to symbolize protesting prohibition has taken a joyful turn this year

Today is 420 — a day that cannabis activists associate with the aroma of protest and lighting up in defiance of the law, but on this last April 20 before prohibition is lifted in Canada, many say it's a day to celebrate.

"We're the first G20 country to have a legal recreational cannabis market. It's a moment for Canada to be proud of what's to come," says Josh Lyon, vice-president of marketing at Hiku Brands, which not only owns licensed cannabis producers, but the Tokyo Smoke chain of cannabis lifestyle stores.

New figures from Statistics Canada provide some of the clearest pictures of cannabis consumption in the country to date

People marking 4/20—national weed day—this year are more likely to reach for the traditional dried cannabis product than for a vape pen, according to new survey results from Statistics Canada.

Edibles were the second most common product, followed by hashish.

The results are from the first round of a new survey from the statistical agency which looks at who’s consuming cannabis, how they’re getting it, what products they’re using and how they’re behaviour might change after legalization. It provides one of the clearest pictures of cannabis consumption in the country to date.

Here’s a rundown of some of the other results: