1.

计算两个日期之间相差几天几小时几分钟

　　NSDateFormatter *dateFormatter=[[NSDateFormatter alloc] init];

   [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];

   NSDate *  senddate=[NSDate date];

   //结束时间

   NSDate *endDate = [dateFormatter dateFromString:@"2014-6-24 00:00:00"];

   //当前时间

   NSDate *senderDate = [dateFormatter dateFromString:[dateFormatter stringFromDate:senddate]];

   //得到相差秒数

   NSTimeInterval time=[endDate timeIntervalSinceDate:senderDate];

   int days = ((int)time)/(3600*24);

   int hours = ((int)time)%(3600*24)/3600;

   int minute = ((int)time)%(3600*24)600/60;

   if (days <= 0&&hours; <= 0&&minute; <= 0)

       dateContent=@"0天0小时0分钟";

   else

       dateContent=[[NSString alloc] initWithFormat:@"%i天%i小时%i分钟",days,hours,minute];