"If a nation works 6 days a week, 12 hours a shift then obviously they will outcompete any nation where people work 5 days a week for 8 hours." - This is not obviously true to me, can you explain why it is for you?
Does the same hold for going from 5 days to 7 days or 8 hours to 16 hours?
A reasonable person should agree at some point adding more time will make people less productive due to lack of breaks, rest, etc.
Is it obvious where the line is? if so, where?
"As of July 2022, more than 80 UK companies and organisations are recognised as having permanently implemented a four-day working week"
"As 50% of workers claim improved productivity during the period, the Manufacturing Technology Centre (MTC) announced it will permanently provide a four-day workweek to its 820 employees"
In, say, China a worker doing 996 will make 720 items. Te average working hours in the Netherlands are 36 hours or so per week. Making 360 items.
As long as there is free trade the Chinese factory will simply outproduce the Dutch one since they utilise their capex better.
Obviously European workers can't be reasonably asked to compete in an open market when labour laws, salary, health inspection etc... in China are at a 1920 Dutch level.
If your factory workers spend twice as long working, it's likely that more widgets will get made. I'm not certain you can generalize too far from that, though.
Tariffs aren't inherently bad, they're a tool.
[1] Caveats apply. For example more advanced machinery with higher stress may necessitate shorter shifts; while highly motivated creative work might permit longer shifts at times.
[2] Adam Smith -for instance- was mostly against tariffs, though he identified certain exceptions such as national defense reasons.
At second approximation, the <Dutch> factory in that example might net make a larger number of items per hour because the workers are more alert and concentrated and make less mistakes. So the <dutch> factory and the <chinese> factory might actually be producing the same number of items.
Of course then there's more steps to this, and you need to start actually looking at systems and what you're optimizing for etc etc.
And, not everything is factories. For instance, if your operator (at eg. Smit or Mammoet) is operating a large crane that's lifting a 100 ton oil platform, maybe you'd prefer them to be wide awake and on the ball, regardless.
This was worked out by David Ricardo 200 years ago. You still benefit from trade even if (granting the argument) you are worse at producing everything.