Is sleeping a little at night (4:00-8:00) everyday for almost a year bad?  

No. There are so called short sleepers who are able to function on 4-6 hours of sleep per night. Limited hours of sleep at night is only bad if your work/academic performance or quality of life is affected the next day.
Sleep hygiene. The average adult does optimally well on 7-8 hours of sleep per night. You also get your most beneficial sleep, when it is any of the hours before midnight. Your hormones production and secretion need you to sleep longer than 4 hours. Do not turn to sleep-aids! Talk to your family medicine doc about this for good help and advice.