如題。
畫個圖分析一下：

程式碼

- (NSDate *)dateAfterMonths:(NSDate *)currentDate gapMonth:(NSInteger)gapMonthCount {
    //獲取當年的月份，當月的總天數
 

    NSCalendar *calendar = [NSCalendar calendarWithIdentifier:NSCalendarIdentifierGregorian];
    NSDateComponents *components = [calendar components:NSCalendarUnitYear|NSCalendarUnitMonth|NSCalendarUnitDay|NSCalendarUnitHour|NSCalendarUnitMinute|NSCalendarUnitCalendar fromDate:currentDate];

    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
    [formatter setDateStyle:NSDateFormatterFullStyle];
    [formatter setDateFormat:@"yyyy-MM-dd"
 
];
//    [formatter setTimeZone:[NSTimeZone localTimeZone]];
//    [formatter setTimeZone:[NSTimeZone timeZoneWithName:@"Asia/Shanghai"]];

    NSString *dateStr = @"";
    NSInteger endDay = 0;//天
    NSDate *newDate = [NSDate date];//新的年&月
    //判斷是否是下一年
    if (components.month+gapMonthCount > 12) {
        //是下一年
 

        dateStr = [NSString stringWithFormat:@"%zd-%zd-01",components.year+(components.month+gapMonthCount)/12,(components.month+gapMonthCount)%12];
        newDate = [formatter dateFromString:dateStr];
        //新月份的天數
        NSInteger newDays = [calendar rangeOfUnit:NSCalendarUnitDay inUnit:NSCalendarUnitMonth forDate:newDate].length;
        if ([self isEndOfTheMonth:currentDate]) {//當前日期處於月末
            endDay = newDays;
        } else {
            endDay = newDays < components.day?newDays:components.day;
        }
        dateStr = [NSString stringWithFormat:@"%zd-%zd-%zd",components.year+(components.month+gapMonthCount)/12,(components.month+gapMonthCount)%12,endDay];
    } else {
        //依然是當前年份
        dateStr = [NSString stringWithFormat:@"%zd-%zd-01",components.year,components.month+gapMonthCount];
        newDate = [formatter dateFromString:dateStr];
        //新月份的天數
        NSInteger newDays = [calendar rangeOfUnit:NSCalendarUnitDay inUnit:NSCalendarUnitMonth forDate:newDate].length;
        if ([self isEndOfTheMonth:currentDate]) {//當前日期處於月末
            endDay = newDays;
        } else {
            endDay = newDays < components.day?newDays:components.day;
        }

        dateStr = [NSString stringWithFormat:@"%zd-%zd-%zd",components.year,components.month+gapMonthCount,endDay];
    }

    newDate = [formatter dateFromString:dateStr];
    return newDate;
}

//判斷是否是月末
- (BOOL)isEndOfTheMonth:(NSDate *)date {
    NSCalendar *calendar = [NSCalendar calendarWithIdentifier:NSCalendarIdentifierGregorian];
    NSInteger daysInMonth = [calendar rangeOfUnit:NSCalendarUnitDay inUnit:NSCalendarUnitMonth forDate:date].length;
    NSDateComponents *componets = [calendar components:NSCalendarUnitDay fromDate:date];
    if (componets.day >= daysInMonth) {
        return YES;
    }
    return NO;
}

發現個問題，如上方法得到的日期是GMT時間，直接在datePickerView中顯示的話是正常的（當然前提是datePickerView本地化），但是打印出來就是GMT時間，設定timezone也無用。