How can I use month name as contextual filter?
You can programmatically alter the contextual filter value of "january" to "01 - 12" in hook_views_pre_view

/*
 * Implements hook_views_pre_view()
 */
function mymodule_views_pre_view(ViewExecutable $view, $display_id, array &amp;$args) {
  // Modify contextual filters for my_special_view.
  if ($view-&gt;id() == 'my_special_view') {
    // insert here some php magic to format "January" to "01".
    $og_arg = t('@og_arg', ['@og_arg' =&gt; $args[0]], ['langcode' =&gt; 'en']);
    $date = date_parse($og_arg);
    // assign formatted value.
    $args[0] = $date['month'];
  }
}