只要這么做就不會再浪費更多美好的生命在處理這件事情上，如下所示...

Swift 1.x

        let date = NSDate()
        let calendar = NSCalendar.currentCalendar()
        let components = calendar.components(.CalendarUnitDay | .CalendarUnitMonth | .CalendarUnitYear, fromDate: date)
        
        let year =  components.year
        let month = components.month
        let day = components.day

Swift 2.x

        let date = NSDate()
        let calendar = NSCalendar.currentCalendar()
        let components = calendar.components([.Day , .Month , .Year], fromDate: date)
        
        let year =  components.year
        let month = components.month
        let day = components.day
        
        print(year)
        print(month)
        print(day)

Swift 3.x

//作為 swift 3 的一個特色，蘋果移除了 NS，讓代碼更簡單了
//現在的代碼會是：
 
let date = Date()
let calendar = Calendar.current
 
let year = calendar.component(.year, from: date)
let month = calendar.component(.month, from: date)
let day = calendar.component(.day, from: date)

可以使用這里提供的多個變量來組成多種日期組件：https://developer.apple.com/reference/foundation/nsdatecomponents