title: error: uint64_t was not declared in this scope when compiling C++ program
body: <p>I am trying out a simple program to print the timestamp value of <code>steady_clock</code> as shown below:</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include &lt;chrono&gt;
  using namespace std;
  int main ()
  {
    cout &lt;&lt; "Hello World! ";
    uint64_t now = duration_cast&lt;milliseconds&gt;(steady_clock::now().time_since_epoch()).count();
    cout&lt;&lt;"Value: " &lt;&lt; now &lt;&lt; endl;
  
    return 0;
  }
  </code></pre>
  
  <p>But whenever I am compiling like this <code>g++ -o abc abc.cpp</code>, I am always getting an error:</p>
  
  <pre><code>In file included from /usr/include/c++/4.6/chrono:35:0,
                   from abc.cpp:2:
  /usr/include/c++/4.6/bits/c++0x_warning.h:32:2: error: #error This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options.
  abc.cpp: In function âint main()â:
  abc.cpp:7:3: error: âuint64_tâ was not declared in this scope
  abc.cpp:7:12: error: expected â;â before ânowâ
  abc.cpp:8:22: error: ânowâ was not declared in this scope
  </code></pre>
  
  <p>Is there anything wrong I am doing?</p>