Columns of type date are rendered in the admin via the block Mage_Adminhtml_Block_Widget_Grid_Column_Renderer_Date
. If you look into this block you will see the function for rendering render
and in this function you see that the date is formatted using the call to $format = $this->_getFormat();
.
Having looked at the function _getFormat
you can see that is simply gets the format attribute from the column and when one is not set it defaults.
/**
* Retrieve date format
*
* @return string
*/
protected function _getFormat()
{
$format = $this->getColumn()->getFormat();
if (!$format) {
if (is_null(self::$_format)) {
try {
self::$_format = Mage::app()->getLocale()->getDateFormat(
Mage_Core_Model_Locale::FORMAT_TYPE_MEDIUM
);
}
catch (Exception $e) {
Mage::logException($e);
}
}
$format = self::$_format;
}
return $format;
}
So what you should be able to do is when adding your column simply set the attribute format
to how you want your date to be shown.