nsdate 前一天 后一天

http://blog.sina.com.cn/s/blog_6568e7880100kfnh.html -(IBAction)prevDay:(id)sender{

       NSDateFormatter *format = [[NSDateFormatter alloc] init];
       [format setDateFormat:@"yyyy-MM-dd"];
       NSString * reportDate = [format stringFromDate:self.m_dataPicker.date];
       NSDate *date = [format dateFromString:reportDate];
       NSDate *newDate = [[NSDate alloc] initWithTimeIntervalSinc eReferenceDate:([date timeIntervalSinceReferen ceDate] - 24*3600)];
          reportDate = [format stringFromDate:newDate];
       [m_pickerButton setTitle:[[NSString alloc] initWithString:reportDate] forState:UIControlStateNormal];
       [m_dataPicker setDate:newDate animated:NO];
     
       [format release];
}

-(IBAction)nextDay:(id)sender{
       NSDateFormatter *format = [[NSDateFormatter alloc] init];
       [format setDateFormat:@"yyyy-MM-dd"];
       NSString *reportDate = [format stringFromDate:self.m_dataPicker.date];
       NSDate *date = [format dateFromString:reportDate];
       NSDate *newDate = [[NSDate alloc] initWithTimeIntervalSinc eReferenceDate:([date timeIntervalSinceReferen ceDate] + 24*3600)];
            reportDate = [format stringFromDate:newDate];
      
       [m_pickerButton setTitle:[[NSString alloc] initWithString:reportDate] forState:UIControlStateNormal];
       [m_dataPicker setDate:newDate animated:NO];
     
      
       [format release];
}