Nuria Chinchilla is anti-siesta. It’s 15.00 in Barcelona, the time when every shady bench is taken up by snoozing Catalans. But Chinchilla – a professor in the department of managing people in organisations at Navarra’s IESE Business School – won’t be sleeping; for she has more pressing concerns to discuss.

Chinchilla explains that the Spanish afternoon nap is actually a relic from the civil war-ravaged years of the 1930s. “It comes from a time when people were doing two jobs,” she says. “Siesta culture does not fit with modern life. A two- or three-hour lunch is not family friendly; it means we are working too late. How can you expect people to function as mothers, fathers and husbands when they are working until nine at night? We need a different, more condensed day. But in Spain, culture is very slow to change.”

In fact, the whole of the industrialised world has been slow to update the shape of its working day. In 1930 the economist John Maynard Keynes predicted that by the 21st century Europeans would enjoy a 15-hour week. He reasoned that with our sci-fi innovations and high wages, there would be no need for the 40-hour grind. But the pace of change has been glacial. In Europe, mean working hours did decrease until the 1970s, but then surged again in the 1980s, and now hover at around 37 hours a week. (In large parts of Europe, however, they are edging down.)

For all the talk of micro-jobs and “flexitime”, the vast majority of the world’s working population still follow a classic nine-to-five formula. EU data from 2010 also shows a cruel inversion: while hours stay more or less the same, work continues to get more intense and stressful. Computerised gadgetry, multi-tasking and modern target-driven management styles mean we pack more tasks into the working day. We’ve absorbed all the streamlining advancements, but stuck to a template of the past.

That’s because the working week is entrenched in culture – from culinary rituals to religious work ethic – and is very difficult to shift. In Japan, where a long-hours malaise is endemic, several recent court rulings have resulted in big car giants such as Toyota paying out large sums to the wives of salaried men who officially died of karoushi (yes, they have a special word for “death from overwork”) – but the punishingly industrious culture has been largely resistant to reform. The toxic mix of office politics, fierce company loyalty and peer pressure has turned work into an unshakable cult.

“People are nervous about leaving the office before others in the evening. No matter how pressing family commitments may be, nobody will leave before the boss,” says Jenny Holt, a professor at Meiji University, Tokyo. “In some government offices it’s usual to work until midnight or just sleep under your desk. Family life suffers, marriages end up as nothing more than two people sharing a house. [And] the population is plummeting – for obvious reasons.”

Often half-hearted state interventions are a good indicator of how bad it’s got. In South Korea, which has some of the longest working hours in the world at 2,316 a year (the German average is 1,141, according to figures from the International Labour Organization), the government has introduced a “procreation day”, where managers snap out the lights in government offices at 19.00, telling their employees to go home and spend time with their families – or make them bigger.

Should Europe worry that South Koreans are working fiendishly long hours while the French sip viognier over long lunches? The simple answer is no. Long hours are often connected in Europe with low productivity. Many wonder if, as productivity rises in Asian economies, working hours will come down. “Over time, as Korea’s productivity rises they will get richer and buy more of everything they like, including leisure, so gradually they will tend to work fewer hours,” says Donald Robertson, senior lecturer in macroeconomics and finance at Pembroke College, Cambridge.

But what if they catch up in technology and productivity and still choose to work super-long hours? That won’t matter either, says OECD economist, Paul Swain. “In that case South Korea would end up with higher output per worker. But its society would choose a life with no free time or leisure. And no time to spend their wealth. “Already, for instance, the French work a lot less than the Americans. [Both countries have very similar productivity scores.] So, they are a lot less affluent. But this is a cultural consensus in France. It is a lifestyle choice.”

A country’s working hours are often a result of a kind of national negotiation with its values. The Netherlands’ low-hours culture (where men on average work 37 hours a week and women just 26) is linked to its conservative heritage and its distrust of paid-for childcare. “The Dutch have a traditional role for mothers which has become enshrined in law,” says Jon Messenger, co-author of ILO publication Working Time Around the World. “Studies show that well over half of Dutch women work part-time hours. They’ve created rewarding, high-status part-time jobs. What’s interesting here is that men are now starting to work part-time too.”

Other cultures are more rigid. In fact, what’s hailed as flexitime often means just a slight adjustment to the normal working rhythm. In the US (which clocks up an average of 1,792 hours a year) big firms and even civic authorities have had great success by tinkering, ever so slightly, with the nine-to-five formula. In one citywide trial in Houston, Texas, dubbed “Flex in the City”, workers were asked to stagger their morning start time to reduce rush-hour traffic jams on commuter routes. The trial might have only made minuscule modifications to working life, but proved so successful it was found to slash workers’ stress by 58 per cent.

But for many, the real meaning of “flex” is onerous multitasking or just unpaid overtime. This is especially true for women. Recent Finnish studies show that white-collar women found flexible regimes nearly four times more irksome than helpful. Just as long hours don’t always make for better productivity, flexible working hours don’t always equal progress. “You could say that one of the tricks managers have played on us is flexibility,” says Brendan Burchell, senior lecturer of sociology at Cambridge University. “They’ve created a very grey area. Even if trade unions did want to regulate this, it would be very difficult.”

The workplace has reached a critical moment. Globalised, modern economies need to find a way to nurture a slick, competitive workforce without treating them like machines. The contagious buzz of frantic workaholism needs a firm hand. Managers need to discourage presenteeism and promote productive, healthy hours – a move which could be the key. This might even mean reintroducing a more languorous pace back into the office.

As the Texan study showed, a small amount of flexible time can go a long way – but that doesn’t mean we should do away with the traditional nine-to-five paradigm. In many ways, working rhythms function to protect family and civic life. “There are good reasons we have these structures,” says Burchell. “For a lot of things to work, like going to church or playing football on a Saturday afternoon, it involves people working at the same time. It would be a big mistake to assume we should have unlimited choice.”

But where does this leave the 24-hour economy? As consumers get more and more demanding, unusual working hours may become inevitable. Unless anaemically-lit mini supermarkets are going to rule the world, shops may well have to extend their opening hours. The modern shopper wants to buy ingredients from a local grocer on the way home from work. In the future they may even want to buy a new suit at midnight. “If this trend continues, people working in service industry jobs such as shop assistants will be left very vulnerable,” says Alexandra Beauregard, at LSE’s department of management. “The care sector is geared towards nine-to-five. Will we need nurseries to open 24-hours a day?” Perhaps.

Without a nine-to-five framework flexi-workers only have their judgment – and a few steadfast national habits – between them and a constant stream of winking BlackBerries. Technology has created a dexterous workforce who can dice ingredients for their evening meal while checking their iPhones – but wise companies should reinstate the line between work and home. Some countries, such as food and drink-focused France, have more social ballast than others. “I’ve seen it in American films,” adds the French Eurofound researcher, Agnès Parent-Thirion. “This ‘having a sandwich at your desk’. For me, this is not eating. Most French people will always take time to sit down and have lunch.”

Back in Barcelona, Professor Chinchilla has another cure for Spain’s dilemma – shorter days altogether. She hails “family responsible” companies such as the energy giant Iberdrola, that recently restructured their working day to allow employees to go home at 15.30. “Immediately they found that absenteeism went down, as did accidents – and meanwhile productivity went up,” she says. “Spanish people desperately want a more condensed day. They don’t want to hang around for two hours at lunch. They want to be at home making sure their children are doing well at school and their marriages are in check.”

Let’s hope Chinchilla’s condensed, family-friendly day doesn’t backfire and leave Spaniards disgruntled and chomping a sandwich at their desks.