How to check whether the selected time range already exists into the database or not

I m trying to insert the from time and to time from text box,before insert i m checking whether the same time exists into the given database, here i m giving a 1 hr gap also before insertion, example 6:00 am to 11:00 am '12:00 pm to 4:00 pm' '5:00 pm to 9:00 pm' '10:00 pm to 2:00 am' 3:am to 5:00 am (here every time slot is having a 1 hr gap)in this way before insertion it should check any conflicts occurs if yes display a alert message.Using my code i m able to insert and check conflicts till 10:00 pm to 2:am , later when i try to insert 11:00 pm to 4:am it should display already exists rather the values are getting inserted

Please help