title: "String was not recognized as a valid DateTime.” error occurs for some exact dates
body: <p>I have a problem <strong>converting Gregorian calendar dates to Persian(Hijri calendar) using default system "en-GB" culture</strong> in my ASP.NET MVC Application.
  I used the globalization tag in my web.config so the default culture would be "en-GB":</p>
  
  <pre><code>    &lt;system.web&gt;
          ...
          &lt;globalization uiCulture="en-GB" culture="en-GB" /&gt;
          ...
      &lt;/system.web&gt;
  </code></pre>
  
  <p>The conversion will happen for any date except for these exact dates that I listed them below and will throw <strong>"String was not recognized as a valid DateTime.”</strong> error.</p>
  
  <p><strong>The exact dates that will throw exception are:</strong></p>
  
  <ol>
  <li>22/07/(any year)</li>
  <li>22/09/(any year)</li>
  <li>19/05/(any year)</li>
  <li>20/05/(any year)</li>
  <li>21/05/(any year)</li>
  </ol>
  
  <p>A part of my sample code:</p>
  
  <pre><code>using System.Globalization;
      ...
      ...
      public static PersianCalendar PC = new PersianCalendar();
      ...
  
      //I'm using this method for conversion
      public static DateTime GregorianToPersian(DateTime date)
      {
                  ...
  
                  string stringDate = string.Format("{0}/{1}/{2} {3}:{4}:{5}"
                      , PC.GetDayOfMonth(date), PC.GetMonth(date), PC.GetYear(date)
                      , PC.GetHour(date), PC.GetMinute(date), PC.GetSecond(date));
                  return DateTime.Parse(stringDate); //error!
      }
  </code></pre>
  
  <p>Hope you guys can help me out with.
  <em>Thanks.</em></p>