title: validate unix timstamp in controller by laravel validation
body: <p>is there anyway to validate incoming unixtime's parameter to server and compare that second one is greather that first one by laravel validation? 
  my code only validate date format</p>
  
  <pre><code>$this-&gt;validate($request, [
              'start_date'    =&gt; 'required|date',
              'end_date'   =&gt; 'required|date|after_or_equal:start_date',
  
          ]
  </code></pre>