title: Why does coliru return the same values for chrono::system_clock::now().time_since_epoch()?
body: <p>While testing someone else's code on coliru, I noticed that <code>std::chrono::system_clock::now().time_since_epoch()</code> returns the same values on multiple runs. I tested the following code with g++ and clang++ on <a href="http://coliru.stacked-crooked.com/a/a558e180e6658e6d" rel="nofollow">coliru</a>.</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include &lt;chrono&gt;
  int main()
  {
      auto seed = std::chrono::system_clock::now().time_since_epoch().count();
      std::cout &lt;&lt; seed &lt;&lt; "\n";
      std::cout &lt;&lt; std::chrono::system_clock::now().time_since_epoch().count() &lt;&lt; "\n";
  
      return 0;
  }
  </code></pre>
  
  <p>Output:</p>
  
  <blockquote>
    <p>g++ -std=c++11 -O2 -Wall -pedantic -pthread main.cpp &amp;&amp; ./a.out</p>
    
    <p>1433249917642594133</p>
    
    <p>1433249917642674289</p>
  </blockquote>
  
  <p>It does work as expected on <a href="http://ideone.com/eiDtH5" rel="nofollow">ideone</a> and obviously on my computer.</p>
  
  <p>Does anyone know why coliru returns the same values on every run?</p>