iOS Why do I get "2010-01-01 00:00:00 +900" from "2010-12-31 15:00:00 +000"?

[mikezang]

I have NSDate, it will be shown as below if I used NSLog(@"%@", date.description);
2010-12-31 15:00:00 +0000

it will be shown as if I used NSLog(@"%@", [date descriptionWithLocale:[[NSLocale currentLocale] localeIdentifier]]);
Saturday, January 1, 2011 12:00:00 AM Japan Standard Time

But it will be show as below if I used NSLog(@"%@", [date formattedDateString]);
2010-01-01 00:00:00 +0900

- (NSString *)formattedDateString {
    return [self formattedStringUsingFormat:@"YYYY-MM-dd HH:mm:ss ZZZ"];
}
 
- (NSString *)formattedStringUsingFormat:(NSString *)dateFormat {
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:dateFormat];
    NSString *ret = [formatter stringFromDate:self];
    [formatter release];
    return ret;
}

Where do I make mistake?

 

[mikezang]

I got what I need if I used NSLog(@"%@", [date formattedDateString]);
2011-01-01 00:00:00 +0900

- (NSString *)formattedDateString {
    return [self formattedStringUsingFormat:@"yyyy-MM-dd HH:mm:ss ZZZ"];
}