When Frank Sinatra sang about “a city that never sleeps”, he probably wasn’t thinking about the economic boost that busy nightlife can provide to a metropolis.

Yet a growing number of cities around the world are increasingly homing in on ways to strengthen their night-time economy.

Around 100 cities now have some form of “night mayor” or “night tsar” in place, to spur this work.

But most of those cities, including London, Sydney, and Sinatra’s beloved New York, are not up all night. In other words, they don’t allow bars and nightclubs to remain open, and serve alcohol, 24 hours a day.

Nonetheless, later this year, Montreal – Canada’s second-largest city – is planning to take the leap into 24-hour nightlife.

Following in the footsteps of Berlin and Tokyo, venues in a new all-night district in Montreal’s city centre will be licensed to remain open, and serve alcohol, throughout the night.

City officials say the move will bring in hundreds of millions of dollars in additional revenue. Currently bars and clubs in the city have to close by 3am.

On a warm Friday evening in July, the centre of Montreal is bustling; busy bars and restaurants line the wide, pedestrianised streets.

“This is an opportunity for economic growth,” says Ericka Alneus, the city councilor behind the 24-hour plan.

“But it’s also to present, and reinforce, the cultural scene.”

In 2022, the annual financial value of Montreal’s nightlife was estimated to be worth C$2.25bn ($1.6bn; £1.3bn), according to advocacy group MTL 24/24. It says that from this, C$121m went in tax to the government.

Clearly, Ms Alneus hopes those figures will increase when venues are allowed to stay open all night.

But not everyone is supportive of the change: “We don’t have enough security for it,” says one concerned reveller.

A fellow citizen is worried about the practical implications: “It’s nice for people who like to party, but the Metro closes at 1.30am,” she says. “There has to be some kind of way people can go back home.”

Sergio Da Silva’s live music bar, Turbo Haus Club, is located on Saint Denis Street in Old Montreal. He says the planned changes haven’t been sufficiently considered.

“You can’t just say, ‘here are some 24-hour bars, go nuts!’.

“There’s no infrastructure to uphold it. There’s no 24-hour public transport, there’s no extra security.

“Then, there’s the cost of living. If people can’t afford to go out, no matter what 24-hour policy you put in, it doesn’t change anything,” he adds.

As the sun sets outside a different bar, L’ile Noir, owner Michelle Lavellee disagrees – he has a different take on the closing-time situation.

“In Montreal, we close at 3am. People are drunk at 1am – and they’re super-drunk at 3am.

“One of the problems we have is, at 3am it’s like madness. But if you expand the hours, there’s less problems, less demand for security,” he explains.

Ms Alneus agrees. She says the fact that so many bars and clubs all currently close at 3am presents problems for the police.

She believes by allowing 24-hour drinking, those venues that don’t wish to stay open all night will be able to close at different times across the night.

She maintains staggering closing time will bring “a bit more safety in nightlife areas”.

Back in 2012, the Dutch capital, Amsterdam, became the first city to appoint a night mayor – a role that went to club promoter and festival organiser Mirik Milan.

He says that during his six years in charge, alcohol-related violence and reports of nuisance fell by 20% and 30% respectively. Those statistics, he says, were vital for local politicians to demonstrate to voters that “we really managed the night in a better way”.

Mr Milan has gone on to co-found VibeLab, a nightlife consultancy advising governments around the world.

He says that when a city embraces nightlife as one of its key cultural assets, it can have billions of dollars of positive impact on the local economy.

“It drives tourism. It brings in a lot of creative operators and businesses that want to be located in that city. And that has a huge impact on the city as a whole.”

Lutz Leichsenring, co-founder at VibeLab, has been instrumental in promoting nightlife as part of Berlin’s Clubcommission – the organisation which, since 2000, has represented approximately 280 nightclubs in the German capital.

“One of the strongest arguments for nightlife is that it attracts talented and skilled workers,” he says.

“It’s just a very important factor why people would relocate to a city, or would like to stay in a city and not move away.”

Mr Leichsenring adds that the increased temperatures brought about by climate change will only make the nighttime economy more important during summer months for many cities.

He maintains everything “from construction, to education, and cultural gatherings” will increasingly move to cooler nighttime hours.

“The night needs to be governed better, because the more you shift to that – to the night – the more conflicts you create, because people also want to sleep at night.”

Meanwhile, efforts to transform cities into all-night zones have – in some cases – proved disappointing.

In 2017, London Mayor Sadiq Khan announced his 24-hour city proposal, appointing US comedian Amy Lamé “to champion nightlife”.

Both were criticised earlier this year after suggesting they had succeeded in their vision, with social media-users expressing their frustration with the hashtag ‘LameLondon’ on X.

The work of Sydney’s night mayor has also faced scepticism.

Sticking to a nightlife plan isn’t always easy, particularly when governments change, says Jess Reia, assistant professor of data science at the University of Virginia.

“The challenge is how to keep good policies after administration change – instead of having a pilot project for a few years, and then ending up with nothing,” she says.

Back in Montreal, there is no start date yet for 24-hour opening. Ms Alneus says the intention is to launch some time in the autumn.

“We are trying to be trailblazers, and to push forward something that everybody enjoys.” she says.

“There are venues, artists, initiatives and performances at night-time that should have the light on them – for the economic growth of the city, but also for the cultural identity of Montreal.”