try this.
NSString *suffix_string = @"|st|nd|rd|th|th|th|th|th|th|th|th|th|th|th|th|th|th|th|th|th|st|nd|rd|th|th|th|th|th|th|th|st";
NSArray *suffixes = [suffix_string componentsSeparatedByString: @"|"];
NSDateFormatter *monthDayFormatter = [[NSDateFormatter alloc] init];
[monthDayFormatter setDateFormat:@"d"];
NSDateFormatter *dateFormateHeader = [[NSDateFormatter alloc]init];
int date_day = [[monthDayFormatter stringFromDate:[NSDate date]] intValue];
NSString *suffix = [suffixes objectAtIndex:date_day];
[dateFormateHeader setDateFormat:[NSString stringWithFormat:@"MMMM d'%@' yyyy' at 'hh:mm a",suffix]];
NSString *prefixDateString = [dateFormateHeader stringFromDate:[NSDate date]];
NSLog(@"%@",prefixDateString);