¿que significa este warninggggg??

[pereztroff]

me refiero a este mensaje--->>
Warning: setlocale(): Passing locale category name as string is deprecated. Use the LC_* -constants instead. in /home/virtual/site101/fst/var/www/cdlinares/mainfile.php on line 565


a partir de la linea 565 contiene-->

function formatTimestamp($time) {
global $datetime, $locale;
setlocale ("LC_TIME", "$locale");
ereg ("([0-9]{4})-([0-9]{1,2})-([0-9]{1,2}) ([0-9]{1,2}):([0-9]{1,2}):([0-9]{1,2})", $time, $datetime);
$datetime = strftime(""._DATESTRING."", mktime($datetime[4],$datetime[5],$datetime[6],$datetime[2],$datetime[3],$datetime[1]));
$datetime = ucfirst($datetime);
return($datetime);
}

............

¿que eta mal? ¿que pasa? me pueden explicar??? gracias.