NSDateComponents *comps = [[NSDateComponents alloc] init];

[comps setDay:day]; // day is 4
[comps setMonth:month]; // month is 4
[comps setYear:2009];

/* Make an NSDate out of it */
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];

NSDate *date = [gregorian dateFromComponents:comps];
NSLog(@"Date: %@\n",date);

/* Calculate the new date */
NSDate *newDate = [date addTimeInterval:60*60*24*offset]; // Offset is 7 here
NSLog(@"New Date: %@\n",newDate);

/* Make a NSDateComponent out of the new date */
NSDateComponents *newDateComponents = [gregorian components:(NSDayCalendarUnit | NSWeekdayCalendarUnit) fromDate:newDate];
NSLog(@"New date seperate components --- Day: %d Month:%d\n",[newDateComponents day],[newDateComponents month]);


2009-05-22 02:00:43.391 [2317:20b] Date: 2009-04-04 00:00:00 +0300
2009-05-22 02:00:43.391 [2317:20b] New Date: 2009-04-11 00:00:00 +0300
2009-05-22 02:00:43.394 [2317:20b] New date seperate components --- Day: 11 Month:2147483647