I'm making a SwiftUI Budget app where user can add a transaction (CoreData entity) and make it recurring by choosing start date and recurrence interval: weekly, every two weeks, monthly, every 3/6 month or yearly. I'm using Picker for both date and interval.

I'm new to app development so at this stage I'm stuck with no solution as to how to implement recurrence. For example I've read about Timer class, but couldn't figure out how to pass recurrence interval ( every month, 3 month etc) to Timer interval to match user current Calendar.

Could someone please help me out with sort of general structure/ idea of what needs to be done/used to implement this?