title: Can std::chrono::from_stream convert string to time_point with microseconds accuracy?
body: <p><strong>TLDR</strong>:</p>
  <pre><code>std::chrono::sys_time&lt;std::chrono::microseconds&gt; tTimePoint;
  std::istringstream stream(&quot;2020-09-16 22:00:00.123456&quot;);
  
  std::chrono::from_stream(stream, &quot;%Y-%m-%d %H:%M:%S&quot;, tTimePoint);
  </code></pre>
  <p>I expected the code above to parse the <code>.123456</code> as microseconds. However, when running this <code>tTimePoint</code> only contains the date and time excluding subseconds.</p>
  <p><em><strong>Longer</strong></em>:</p>
  <p>I am using <em>Visual Studio 2019</em> with the <em>\cpplatest</em> flag on <em>Windows 10</em>.
  I have a simple input where users can define their datetime format for the input.</p>
  <p>Strings can look like <code>2020-09-16T22:00:00.123456</code> or <code>16.09.2020 22:00:00.123456</code> or any other valid datetime format as long as there's a way of describing it using the qualifiers listed in the <a href="https://en.cppreference.com/w/cpp/chrono/system_clock/from_stream" rel="noreferrer">cppreference for std::chrono::from_stream</a>.</p>
  <p>Based on the reference and my previous experience with <code>std::format()</code>(which uses the same formatting) I would assume that <code>%S</code> also parses subseconds.</p>
  <p>I have also tried <code>std::chrono::parse</code> but this does not state that <code>%S</code> would parse subseconds after the decimal. I have tried various different formats and datetime formats to ensure that this issue does not only occur due to some irregular datetime format.</p>
  <p>Is this an error in the <em>cppreference</em> documentation, is this a not fully implemented feature in the Visual Studio implementation or (most likely) am I just simply missing something obvious about this?</p>
  <p>Thank you for any help that I can get!</p>