24 hours is a business day. A lot of people become confused because of business hours and working hours. The working hours are 9.00 am to 5.00 pm while the business hour starts at 12:00 am and ends at 11:59 pm. The business day in the USA runs from Monday to Friday. The work is expected to be completed by the end of the day. There are three traditional working hours in a day and they are typically called "9-5." These hours also apply to every other country in the Western world.