It depends on where you’re getting your recurrences from? I don’t recall any Apple-specific recurrence mechanisms on the level of calendars like you’re describing. But eventually if you have date objects, you’ll want to use DateComponents to extract the kind of data you’re describing (I don’t know what RRules are)
How you get a DateComponents object is below. See the docs for how to extract the individual months, days etc.

let date = Date()
var calendar = Locale.current.calendar
var dateComponents = calendar.dateComponents(Set<Calendar.Component>(), from: date)