Traditional 9-to-5 office hours are becoming a thing of the past, thanks to the changing and more relaxed attitude towards time-keeping by bosses and the widespread use of mobile technology, a new study has shown.

But while this may seem like good news for restless desk jockeys, it doesn't mean they are working fewer hours overall, according to the study by Washington-based data security and backup provider Mozy.

The research involving more than 1,000 employees from US, Britain, Germany, France and Ireland revealed that flexibility in office hours often results in employees working for more than 12 hours instead of the traditional eight hours.

It also found that 73 per cent of bosses have a relaxed attitude toward office hours, since they trust their staff is working long before they reached office, LiveScience reported.

The average boss, it found, is willing to turn a blind eye to employees being up to 32 minutes late and let them spend a quarter of the week working from home. US employers take the most relaxed view, tolerating their staff turning up 37 minutes late in the day.

While the majority of employers don't mind when workers start their days later, they in turn expect flexibility from their employees to work outside of normal business hours, even as they wind down for the night.

The fluid approach to working hours means many employers are now comfortable with calling employees after-hours, with 80 per cent saying they think it's acceptable to call staff in the evening, it said.

The global results showed that the average person starts checking their work email at 7:42 am, gets into the office at 8:18 am, leaves the office at 5:48 pm, and stops working fully at 7:19 pm, meaning employees are "in work mode" for nearly 12 hours a day.

And the death knell for traditional office hours has been sounded by the mobile technology, with 75 percent of employers giving their employees the tools they need to get their jobs done wherever they are, the study found.

"Workers everywhere are making the most of the technology available to them to build more flexibility for work and family," said Russ Stockdale, general manager of Mozy.

"Hard work isn't going unnoticed and mobile working and technology is having more of an impact on employer attitudes than people think. We can see from the research findings that we've come a long way towards work being 'a thing that you do,' rather than 'a place that you go.'"