Delete archivelogs using RMAN until date .....
RMAN delete archive until time
RMAN> run
{
DELETE archivelog until time "to_date('2010-10-08:05:00:00' ,'YYYY-MM-DD:hh24:mi:ss')";
{
DELETE archivelog until time "to_date('2010-10-08:05:00:00'
crosscheck archivelog all;
delete noprompt expired archivelog all;
delete noprompt expired archivelog all;
}