iOS-----------計算兩個時間的時間差

    UIButton * nameButton = [UIButton buttonWithType:UIButtonTypeCustom];

    nameButton.frame = CGRectMake(0, 200, self.view.frame.size.width, 100);

    nameButton.backgroundColor = [UIColor orangeColor];

    [self.view addSubview:nameButton];

    NSCalendar *calendar = [NSCalendar currentCalendar];

    NSDate *starDate = [NSDate dateWithTimeIntervalSince1970:1513142700];//開始時間

    NSDate *endDate = [NSDate dateWithTimeIntervalSince1970:1513146300];//結束時間

    unsigned int unitFlags = NSCalendarUnitYear| NSCalendarUnitMonth | NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond ;

    NSDateComponents *d = [calendar components:unitFlags fromDate:starDate toDate:endDate options:0];

    [nameButton setTitle:[NSString stringWithFormat:@"%ld小時%ld分%ld秒", (long)[d hour], (long)[d minute], (long)[d second]] forState:0];