Body clock

Patient: Hi, its not really a nutrition issue but I guess that was the closest to what I need to know about.I am 12th class student and I am a night worker.I was also in an afternoon school these 2 years.I built a habit of studying till 4 to 5 and then waking up at 11.The thing now is I have my exams at 9 or 10!Do I have to my body clock for better concentration?These are entrance exams and are so very important for my life I don’t want to ruin it for any reason.