計算兩個日期之間差異的問題

Question

我需要計算兩天之間的差異，以分鐘爲單位。

NSDate *now = [[NSDate alloc] init]; 

NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init]; 
    [outputFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"]]; 
    [outputFormatter setDateFormat:@"dd/MM/yyyy hh:mm:ss a"]; 

    NSString* dateStringFromDatabase = @"01/01/1900 11:00:00 AM"; 

    NSDate* dateFromString = [outputFormatter dateFromString:dateStringFromDatabase]; 

NSString* a = [outputFormatter stringFromDate:now]; 
    NSDate* b = [outputFormatter dateFromString:a]; 

    NSCalendar *gregorian = [[NSCalendar alloc]initWithCalendarIdentifier:NSGregorianCalendar]; 

    unsigned int unitFlags = NSHourCalendarUnit | NSMinuteCalendarUnit | NSDayCalendarUnit | NSMonthCalendarUnit; 

    NSDateComponents *components = [gregorian components:unitFlags fromDate:dateFromString 
                toDate:b options:0]; 

    int hours = [components hour]; 
    int minutes = [components minute]; 

    self.lblResult.text = [NSString stringWithFormat:@"%i:%i", hours, minutes]; 

但我有以下問題： 對於當前的時間，我得到：

2012-10-21 07:37:09 +0000 // wrong it's two hours late 

當我嘗試投@"01/01/1900 11:00:00 AM"到NSDate我得到

1900-01-01 10:00:00 +0000 // also two hours late 

Answer 1

您需要設置-dateStyle而不是時間樣式，因爲該字符串中還包含日期。

編輯---

現在，您需要更改-dateFormat到dd/MM/yyyy HH:mm:ss a

Answer 2

我希望這有助於

NSString *dtString = @"1900-01-01T11:00:00"; 
    dtString = [dtString stringByReplacingOccurrencesOfString:@"T" withString:@" "]; 
    NSDate *today = [NSDate date]; 
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; 
    [dateFormatter setDateFormat:@"YYYY-MM-dd HH:mm:ss"]; 
    NSString *currentTime = [dateFormatter stringFromDate:today]; 
    NSDate *toTimeDate = [dateFormatter dateFromString:dtString]; 
    NSString *toTime = [dateFormatter stringFromDate:toTimeDate]; 

Answer 3

試試這個............ ......

如果您在String中有日期，那麼將其轉換爲日期使用@"dd/MM/yyyy hh:mm:ss a"

NSDate *startDate = ...; 
NSDate *endDate = ...; 

現在日期比較

// Date Comparision 
NSCalendar *gregorian = [[NSCalendar alloc]initWithCalendarIdentifier:NSGregorianCalendar]; 

unsigned int unitFlags = NSHourCalendarUnit | NSMinuteCalendarUnit | NSDayCalendarUnit | NSMonthCalendarUnit; 

NSDateComponents *components = [gregorian components:unitFlags fromDate:LastDate 
               toDate:CuurentDate options:0]; 

獲得兩個日期

int months = [components month]; 
int days = [components day]; 
int hours = [components hour]; 
int minutes = [components minute];