End Date showing Wrong

I want to find start date and end date of week I am geting start date but not find right end date of week startDate = NSDate().startOfWeek(2) print(startDate) endDate = startDate.endOfWeek(3) print(endDate)

  I am getting this start date -2016-07-04 06:30:00 +0000
    end date - 5828963-12-20 00:00:00 +0000

   extension NSDate {
        func startOfWeek(weekday: Int?) -> NSDate? {
            guard
                let cal: NSCalendar = NSCalendar.currentCalendar(),
                let comp: NSDateComponents = cal.components([.YearForWeekOfYear, .WeekOfYear], fromDate: self) else { retu nil }
            comp.to12pm()
            cal.firstWeekday = weekday ?? 1
            retu cal.dateFromComponents(comp)!
        }

        func endOfWeek(weekday: Int) -> NSDate? {
            guard
                let cal: NSCalendar = NSCalendar.currentCalendar(),
                let comp: NSDateComponents = cal.components([.WeekOfYear], fromDate: self) else { retu nil }
            comp.weekOfYear = 1
            comp.day -= 1
            comp.to12pm()
            retu cal.dateByAddingComponents(comp, toDate: self.startOfWeek(weekday)!, options: [])!
        }
    }
    inteal extension NSDateComponents {
        func to12pm() {
            self.hour = 12
            self.minute = 0
            self.second = 0
        }
    }