Object C 获取日期

//得到当前的日期   
 NSDate *date = [NSDate date];   
 NSLog(@"date:%@",date);   
    
 //得到(24 * 60 * 60)即24小时之前的日期，dateWithTimeIntervalSinceNow:   
 NSDate *yesterday = [NSDate dateWithTimeIntervalSinceNow: -(24 * 60 * 60)];   
 NSLog(@"yesterday:%@",yesterday);   
NSDateFormatter *formatter =[[[NSDateFormatter alloc] init] autorelease];   
 NSDate *date = [NSDate date];   
 [formatter setTimeStyle:NSDateFormatterMediumStyle];   
 NSCalendar *calendar = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];   
 NSDateComponents *comps = [[[NSDateComponents alloc] init] autorelease];   
 NSInteger unitFlags = NSYearCalendarUnit |    
                       NSMonthCalendarUnit |   
                       NSDayCalendarUnit |    
                       NSWeekdayCalendarUnit |    
                       NSHourCalendarUnit |   
                       NSMinuteCalendarUnit |   
                       NSSecondCalendarUnit;   
 //int week=0;   
 comps = [calendar components:unitFlags fromDate:date];   
 int week = [comps weekday];    
 int year=[comps year];    
 int month = [comps month];   
 int day = [comps day];   
 //[formatter setDateStyle:NSDateFormatterMediumStyle];   
 //This sets the label with the updated time.   
 int hour = [comps hour];   
 int min = [comps minute];   
 int sec = [comps second];   
 NSLog(@"week%d",week);   
 NSLog(@"year%d",year);   
 NSLog(@"month%d",month);   
 NSLog(@"day%d",day);   
 NSLog(@"hour%d",hour);   
 NSLog(@"min%d",min);   
 NSLog(@"sec%d",sec);   
//得到毫秒   
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];   
 [dateFormatter setDateStyle:NSDateFormatterMediumStyle];   
 [dateFormatter setTimeStyle:NSDateFormatterShortStyle];   
 //[dateFormatter setDateFormat:@"hh:mm:ss"]   
 [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss.SSS"];   
 NSLog(@"Date%@", [dateFormatter stringFromDate:[NSDate date]]);   
 [dateFormatter release];