只需傳入兩個日期

/**任意兩天相差天數*/

+ (NSInteger)getTheCountOfTwoDaysWithBeginDate:(NSString *)beginDate endDate:(NSString *)endDate{

NSDateFormatter *inputFormatter = [[NSDateFormatteralloc] init];

    [inputFormatter setLocale:[[NSLocalealloc] initWithLocaleIdentifier:@"en_US"]];

    [inputFormatter setDateFormat

NSDate *startD =[inputFormatter dateFromString:beginDate];

NSDate *endD = [inputFormatter dateFromString:endDate];

// 當前日曆

NSCalendar *calendar = [NSCalendarcurrentCalendar];

// 需要對比的時間資料

NSCalendarUnit unit = NSCalendarUnitYear | NSCalendarUnitMonth

    | NSCalendarUnitDay;

// 對比時間差

NSDateComponents

return dateCom.day;

}