[Koha] Koha calendar hourly settings

Dear All, I am using Koha 3.12 because of its provision to issue items on hourly basis which I need for my 2-hour short-loan services. However, I cannot find any settings on the Koha calendar to help me set working hours for each working day so that users who borrow short-loan items towards the closure of the library say at 10:00pm are not charged overdue fines for the rest of the night and any other times the library remains closed. My calendar is something like: Mondays - Fridays 8:00am-10:pm Saturdays 11:am - 5:00pm Sundays Closed Any ideas on how to go about this? Regards I Juma