add_event_handler('loc_begin_element_set_global', 'change_date_element_set_template_data');
add_event_handler('element_set_global_action', 'change_date_element_action', 50, 2);

function change_date_element_set_template_data()
{
  global $template, $lang;

  $day = empty($_POST['date_available_day']) ? date('j') : $_POST['date_available_day'];
  $month = empty($_POST['date_available_month']) ? date('n') : $_POST['date_available_month'];
  $year = empty($_POST['date_available_year']) ? date('Y') : $_POST['date_available_year'];
  $month_list = $lang['month'];
  $month_list[0]='------------';
  ksort($month_list);

  $template->assign(array(
    'month_list'          => $month_list,
    'DATE_AVAILABLE_DAY'  => (int)$day,
    'DATE_AVAILABLE_MONTH'=> (int)$month,
    'DATE_AVAILABLE_YEAR' => (int)$year,
    )
  );

  $template->set_filename('change_available_date', realpath(dirname(__FILE__).'/change_available_date.tpl'));

  $template->append('element_set_global_plugins_actions', array(
    'ID' => 'date_available',
    'NAME' => l10n('Change available date'),
    'CONTENT' => $template->parse('change_available_date', true),
    )
  );
}

function change_date_element_action($action, $collection)
{
  if ($action != 'date_available')
  {
    return;
  }

  $date_available = sprintf(
    '%u-%u-%u',
    $_POST['date_available_year'],
    $_POST['date_available_month'],
    $_POST['date_available_day']
    );

  $datas = array();
  foreach ($collection as $image_id)
  {
    array_push(
      $datas,
      array(
        'id' => $image_id,
        'date_available' => $date_available
        )
      );
  }

  mass_updates(
    IMAGES_TABLE,
    array('primary' => array('id'), 'update' => array('date_available')),
    $datas
    );
}

{footer_script}{literal}
  pwg_initialization_datepicker("#date_available_day", "#date_available_month", "#date_available_year", "#date_available_linked_date", "#date_available_action_set");
{/literal}{/footer_script}

<div id="set_date_available">
    <select id="date_available_day" name="date_available_day">
       <option value="0">--</option>
      {section name=day start=1 loop=32}
        <option value="{$smarty.section.day.index}" {if $smarty.section.day.index==$DATE_AVAILABLE_DAY}selected="selected"{/if}>{$smarty.section.day.index}</option>
      {/section}
    </select>
    <select id="date_available_month" name="date_available_month">
      {html_options options=$month_list selected=$DATE_AVAILABLE_MONTH}
    </select>
    <input id="date_available_year"
           name="date_available_year"
           type="text"
           size="4"
           maxlength="4"
           value="{$DATE_AVAILABLE_YEAR}">
    <input id="date_available_linked_date" name="date_available_linked_date" type="hidden" size="10" disabled="disabled">
</div>