title: DateTime "ddd" format makes wrong output when on Android
body: <p>I'm building a calendar type table with the abbreviated weekday name on the top. </p>
  
  <p><em>For the next examples, I'll use the following variable:</em></p>
  
  <pre><code>DateTime dateTime = new DateTime( 2017, 06, 22, 18, 00, 00 );
  </code></pre>
  
  <p>If I attempt to do <code>dateTime.ToString( "ddd" )</code>, it outputs <code>Thu</code> in both <em>C# Interactive</em> and Android. But if I do <code>dateTime.ToString( "ddd", CultureInfo.CreateSpecificCulture( "pt-PT" ) )</code> instead, it outputs <code>qui</code> in <em>C# Interactive</em>, as expected, but <code>Quinta</code> in Android. Is this an error within Xamarin / Android, or am I missing something?</p>