NSCalendarUnit
служит для определения шага между датами и обеспечения нормализации дат.
API iOS 8, Swift 2.0
func generateDates(calendarUnit: NSCalendarUnit, startDate: NSDate, endDate: NSDate) -> [NSDate] {
let calendar = NSCalendar.currentCalendar()
let normalizedStartDate = calendar.startOfDayForDate(startDate)
let normalizedEndDate = calendar.startOfDayForDate(endDate)
var dates = [normalizedStartDate]
var currentDate = normalizedStartDate
repeat {
currentDate = calendar.dateByAddingUnit(calendarUnit, value: 1, toDate: currentDate, options: NSCalendarOptions.MatchNextTime)!
dates.append(currentDate)
} while !calendar.isDate(currentDate, inSameDayAsDate: normalizedEndDate)
return dates
}