- (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view, typically from a nib.
  
  //获得现在的时间
  [self currentTime];
}
#pragma -mark -functions
//计算现在的时间
- (void)currentTime
{
  //时间格式
  NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
  [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
  //现在时间
  NSDate * currentdate = [NSDate date];
  NSString * currentDateString = [dateFormatter stringFromDate: currentdate];
  NSLog(@"---currentDateString--%@",currentDateString);
}

2015-10-23 10:15:24.928 计算现在的时间[1607:61610] ---currentDateString--2015-10-23 10:15:24