How to model part time employees.

Hi everyone. I’m currently working on some new systems for HR at work and have got stuck on how to model part time employees work days. My original assumption was that all part time employees would have a weekly repeating work week and I could just have a table that would store the hours that part time employees work on each day. After looking through some old spreadsheets that the system is replacing things are not as simple as I hoped. As well as weekly schedule there are bi-weekly ones. This wouldn’t be too bad and I could still stick to my original plan but store two weeks duplicating the weekly schedules. Things get messy though with the other schedules I’ve spotted. We have employees that have monthly schedules. Some employees that take whole months off a year and some other more interesting work patterns. I am at a loss of how I can cleanly implement this and keep it maintainable. Any ideas?