NSDate wrong output when add day to NSDate

Question

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy-MM-dd"];

NSString *dateString = [dateFormatter stringFromDate:[NSDate date]];
NSLog(@"%@",dateString);


// Retrieve NSDate instance from stringified date presentation
NSDate *dateFromString = [dateFormatter dateFromString:dateString];

// Create and initialize date component instance
NSDateComponents *dateComponents = [[NSDateComponents alloc] init];
[dateComponents setDay:2];

// Retrieve date with increased days count
NSDate *newDate = [[NSCalendar currentCalendar]
                   dateByAddingComponents:dateComponents
                   toDate:dateFromString options:0];

NSLog(@"Original date: %@", [dateFormatter stringFromDate:dateFromString]);
NSLog(@"New date: %@", [dateFormatter stringFromDate:newDate]);

OutPut

   2013-05-17
   Original date: 2013-05-17
    New date: 1412647-09-06

I add 2 day to that. The new date should be "2013-05-19?. Can anyone tell me what I wrong? Thank in advance.

Answer 1

I assume that you forgot to initialize the day variable. If you add

NSUInteger day = 2;

then your code produces the expected result in my test program.

Answer 2

The init methode of NSDateComponents does not initializes the components. Thus, e.g., year is undefined. Form Apple's documentation:

An instance of NSDateComponents is not responsible for answering questions about a date beyond the 
information with which it was initialized. For example, if you initialize one with May 6, 2004,   
its weekday is NSUndefinedDateComponent