I heard healthy adults need between 7 and 9 hours of sleep so sleeping 4 hrs or less than to it may affect your health negatively. I think, you should sleep when your body feels tired and in order for you to do many tasks during the day maybe you could list them down and manage your time accordingly.
I once consulted with a doctor that the ideal sleep time is indeed 7-9 hours per day. Because there are so many benefits that we can feel
if we can get quality sleep. Such as reducing stress, supporting growth for children and maintaining an ideal body weight. But because of
today's demands of work, many people have bedtime very little. I even only have 2-4 hours of sleep a day, I admit I have to change my lifestyle.