$res = mysql_query("SELECT DATE_FORMAT(FROM_UNIXTIME(UNIX_TIMESTAMP(datum)),'%e.%c.%Y') FROM news where id=$edit");
This will give you d.m.yyyy. If you want the date d-m-yyyy, just use '%e-%c-%Y' in your query.
If you want dd.mm.yyyy, then use '%d.%m.%Y' in your query.
Read the link I gave you, it explains a lot.