Like most situations, you will get the wrong answer until you find the right way to ask the question. If the goal is to maximize time spent, then what you have to do is learn how your body works. And your body works in a certain way, you just have to comply. If you fight it, you will get worse results. I'm saying all this because from the question one might believe that you can -choose- your routine. What I've found is that you have to discover it, you have to discover how your body works.

Wake up with the Sun.

Eat.

Internet 1 hour, or other activity that will warm up your brain. (~8:30 am in the summer)

Learn, 2-3 hours for real, maximum 4 hours for the whole activity.

Gym 1 hour.

Shower.

Eat.

Go outside.

Eat, before 18:00 ideally, before 19:00 in practice. Food will keep you awake during the night and you won't be able to wake up with the Sun!

Sleep (~23:00, ~8 hours). You have to choose your bed time depending on when the Sun rises.

Source: 5 years of searching for this + 2 years of doing this, without being paid :|