For most organizations, booking occurrences start and end on the same calendar day.  For organizations that run 24 hours a day or book resources for several continuous days or weeks, the System Settings must be set to allow booking occurrences to cross midnight.   ResSched treats such bookings as running 24 hours a day/7 days a week from the start time to end time.  Bookings that have several occurrences on different days (e.g., 9:00AM to 4:00PM Monday, Tuesday, Wednesday) do not need the cross midnight setting on.  Turning this setting on will require users to enter an end date for every booking and make some views and reports more cluttered, so it should be left off if not needed.