请问怎么查询一个月中特定的一天？

// 设置月份中开始的时间
NSString *str = @"01 - 12 - 2012";
NSDateFormatter *formatter1 = [[[NSDateFormatter alloc] init] autorelease];
[formatter1 setDateFormat:@"dd - MM - yyyy"];
NSDate *date = [formatter1 dateFromString:str];
NSCalendar *gregorian = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSDateComponents *weekdayComponents = [gregorian components:(NSDayCalendarUnit | NSWeekdayCalendarUnit) fromDate:date];
NSInteger weekday = [weekdayComponents weekday];
int weekNumber = 2;
int dayOfweek = 2;
int x = (7 - weekday) * (weekNumber - 1) + dayOfweek;
// 添加第几个星期
if(x < 7)
{
    x += 7 * (weekNumber - 1) + 1;
}
else
{
    x += 7 * (weekNumber - 2) + 1;
}