      * 指定した年の敬老の日を調べる
      */
     internal func oldPeopleDay(year year: Int) -> Int {
-        let cal = NSCalendar.currentCalendar()
+        guard let cal = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian) else {
+            fatalError("can not create Calendar")
+        }
         
         func dateFromDay(day day: Int) -> NSDate? {
             return cal.dateWithEra(AD, year: year, month: 9, day: day, hour: 0, minute: 0, second: 0, nanosecond: 0)

    case Sun, Mon, Tue, Wed, Thu, Fri, Sat

    init?(year: Int, month: Int, day: Int) {
        let cal = NSCalendar.currentCalendar()
        guard let date = cal.dateWithEra(AD, year: year, month: month, day: day, hour: 0, minute: 0, second: 0, nanosecond: 0) else { return nil }
        let weekdayNum = cal.component(.Weekday, fromDate: date)  // 1:日曜日 ～ 7:土曜日
        self.init(rawValue: weekdayNum - 1)

     *
     */
    public func judgeJapaneseHoliday(year: Int, month: Int, day: Int) -> Bool {
        guard let cal = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian) else {
            fatalError("can not create Calendar")
        }
        guard let date = cal.dateWithEra(
            AD, year: year, month: month, day: day, hour: 0, minute: 0, second: 0, nanosecond: 0) else {
            fatalError() // FIXME: throwにしたほうがよい？
