I faced this problem, and I know the answer, but it's going to take some work.
When you sleep early in the morning till late in the afternoon, you;ve set a pattern. So ow do you break this pattern? Well, it's kinda obvious that going to bed early isn't the easiest method. You;re not even sleepy or tired! But try going to sleep as early as you can one night ( even if it's 4:30) and then get up early, say 8-9 or 10( whatever time you need to get up to go somewhere). Set lots of alarms to get you up and don't take any naps in the day. By the time night comes you'll be exhausted and you'll go to bed early and you'll probably wake up at a normal time and then you can set your habit like that
That's what I'd do when summer changed back to college semesters.