title: How to get current date time of the system in seconds
body: <p>How can I get current date time of the systems in seconds in C++?</p>
  
  <p>I tried this one:</p>
  
  <pre><code>struct tm mytm = { 0 };
  time_t result;
  
  result = mktime(&amp;mytm);
  
  printf("%lld\n", (long long) result); 
  </code></pre>
  
  <p>but I got: -1?</p>