To start fit in the day!
This is different from person to person. But you should not sleep under 6 hours (otherwise you have little energy in my opinion)
and not different every day. Otherwise you have no good sleeprythm. ✨
In my opinion, this question is very relative! It is known to be people and professions like my dad, who once has early service, then started again at noon and then he has night service again. My dad is a driver of profession and therefore this is not so easy to answer when he is to go to bed.
What is important, how good sleep is and how long.
It always depends on when you have to get up the next day,But I think the 21: 30-22: 00 is a good and balanced average.
9h before you get up.
The duration and regularity I think I decisive.