<code>

• (void)timeWithStr:(NSString )str{
  <code>
  NSDate dat = [NSDate dateWithTimeIntervalSinceNow:0];
  NSTimeInterval a=[dat timeIntervalSince1970]1000;
  NSInteger b = (NSInteger)a;//当前系统时间戳
  NSInteger x = [str integerValue];
  NSInteger d = (x -b);
  CGFloat tep = 2460601000;//tep 表示一天
  if (x > tep) { //显示天数
  NSInteger day = floor((d/tep));//向下取整
  [self.surplusButton setTitle:[NSString stringWithFormat:@"剩余:%ld天",day] forState:UIControlStateNormal];
  }else{//进入倒计时
  //进入倒计时后将(毫秒数差)转成小时取整,分取整,秒取整
  self.timeSec = d/1000;
  [self startTimer];
  }
  </code>
  }
• (void)startTimer

{
<code>
if (timer) {
[timer invalidate];
}
timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(refreshLessTime) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:timer forMode:UITrackingRunLoopMode];
</code>
}

• (void)refreshLessTime{
  <code>
  [self.surplusButton setTitle:[NSString stringWithFormat:@"剩余:%02ld:%02ld:%02ld",self.timeSec/3600,self.timeSec%3600/60,self.timeSec%60] forState:UIControlStateNormal];
  </code>
  self.timeSec--;
  if (self.timeSec==0) {
  [self.surplusButton setTitle:@"已结束" forState:UIControlStateNormal];
  self.surplusButton.backgroundColor = [UIColor lightGrayColor];
  [timer invalidate];
  timer = nil;
  }
  }
  </code>