title: Convert a TValue into TDateTime
body: <p>How can I convert a TValue in TDateTime?</p>
  
  <p>I see there are methods like AsInteger, AsDouble, etc. but nothing for TDateTime.</p>
  
  <pre><code>var
    c : TRttiContext;
    t : TRttiType;
    f : TRttiField;
    fieldValue : TValue;
    fieldDateValue : TDateTime;
  begin
    c := TRttiContext.Create;
      t := c.GetType(Self.ClassType);
      for f in t.GetFields do begin
        fieldValue := field.GetValue(Self);
        //convert the TValue in TDateTime
      end;
  end;
  </code></pre>