NSCalendarDate bug?

[Rob Burns]

The small program to calculate age, that follows, usually returns the 
right answer. But, given a birthdate of 1981/9/23 it will return:

2003-09-08 21:42:38.591 age[3987] Age = 22 years, -1 months, 15 days

(because it uses 'todays date' to do the calculation, its probably 
worth noting that I ran it on 2003/9/8)

Is there something wrong in the program, or is that a bug?

Rob

#include <Foundation/Foundation.h>

int main (int argc, char **argv)
{
  NSArray *args;
  NSAutoreleasePool *pool;

  NSString  *dateString;
  NSCalendarDate *birthday, *todaysDate;

  int years=0, months=0, days=0;

  pool = [NSAutoreleasePool new];
  args = [[NSProcessInfo processInfo] arguments];

  if([args count] < 1)
  {
    NSLog(@"I think you forgot something");
    [pool release];
    exit(0);
  }

  dateString = [NSString stringWithString: [args objectAtIndex: 1]];

  birthday = [NSCalendarDate dateWithString: dateString 
calendarFormat: @"%Y/%m/%d"];
  todaysDate = [NSCalendarDate calendarDate];
  [todaysDate years: &years months: &months days: &days hours: NULL
    minutes: NULL seconds: NULL sinceDate: birthday];

  NSLog(@"Age = %i years, %i months, %i days", years, months, days);

  [pool release];
  exit(1);
}