extension NSDate{
    func Year() -> Int {
        let curCalendar:NSCalendar = NSCalendar.currentCalendar()
        let componentYear:Int = curCalendar.component(NSCalendarUnit.Year,fromDate: self)
        return componentYear
    }
    
    //11
    func Month() -> Int {
        let curCalendar:NSCalendar = NSCalendar.currentCalendar()
        let componentMonth:Int = curCalendar.component(NSCalendarUnit.Month,fromDate: self)
        return componentMonth
    }
    
    //28
    func Day() -> Int {
        let curCalendar:NSCalendar = NSCalendar.currentCalendar()
        let componentDay:Int = curCalendar.component(NSCalendarUnit.Day,fromDate: self)
        return componentDay
    }
}

通过扩展NSDate，可以获取当前年月日时间。

主要思路还是通过NSCalendar获取。