WHEN someone works isn't a fundamental issue. IF we're talking retail, thats an obvious exception. If we're talking a job where the employee isnt directly contacting customers, then the time they work is largely less important. The most efficient team I've worked on in my career was made up from people around the world, there were 9 of us, everyone single one was in a different timezone, some 12 hours off from each other... and we got more done as a team than any Team I've been on before or sense... and it was largely due to the nature of our hours... we had to make sure we buttoned our shit up, we documented it well, we communicated VERY efficiently and effectively... etc.
I know it doesn't work for every position at every company, no single thing does, but to consider 9-5 (or any set schedule in particular) "fundamental" to business is short-sided at best...