How to use time

A whole day is 24 hours.
Assuming that we need to sleep for 8 hours for our health, it is 16 hours in a whole day which is saved for us to use time freely.
In Japan the law (Labour Standards Law) prohibits as a rule that employers work labors and workers for more 8 hours a day (for more 40 hours a week).
(Here many of them work and labor at least between 9 a.m. and 5 p.m.)
So in Japan there are just 8 hours left for labors and workers to use freely in a whole day.

In fact we students are neither labors or workers in the sense that what we do is to study and we do not earn money as the value of labor.
But I think that we student, especially in master or doctor course, must study for more 8 hours.
Because in Japan some of labors and workers who begin to work after graduating university in bachelor course (when they are 22 years old or more) are as old as we or younger than we (I am now 25 years old).

By the way it takes 1.5 hours to go to my university from my house, 3 hours to and from my university.
If I would study for 8 hours at my laboratory in the university (with 3 hours of going to and from university) and sleep for 8 hours at home, there are just few 5 hours saved for me in a whole day.
So I must do my housework (e.g. washing, cooking, shopping, eating and so on) in a 5 hours a day.
It could not be impossible but very hard.

I can save time if I cut 2 or 3 hours from my sleeping time while my health may be hurt.
Or I can do it if I give up writing my blog, moreover in English (haha! orz).
(In fact it take 1 hour or more to write my blog every time.)