Something

$where = "birthday eq '01-30-2008'";
$allUsers       = xarModAPIFunc('dynamicdata','user','getitems',
        array(
        'module' => 'roles',
        'itemtype' => 0,
        'join' => 'xar_roles',
        'fieldlist' => array('email','birthday','uid'),
        'where' => $where,
        'sort' => 'birthday',
        'numitems' => '200',
        'startnum' => '1'
        )
);