Just use dates and a little maths
SQL> set serverout on;
SQL>
SQL> DECLARE
2
3 v_start DATE;
4 v_end DATE;
5
6 BEGIN
7
8 v_start := SYSDATE;
9 Dbms_Lock.sleep(10);
10 v_end := SYSDATE;
11
12 Dbms_Output.put_line('Start : ' || To_Char(v_start ,'dd.mm.yyyy hh24:mi:ss'));
13 Dbms_Output.put_line('End : ' || To_Char(v_end ,'dd.mm.yyyy hh24:mi:ss'));
14 Dbms_Output.put_line('Duration : ' || Round((v_end - v_start) * 60 * 60 * 24));
15 END;
16 /
Start : 17.04.2008 17:38:22
End : 17.04.2008 17:38:32
Duration : 10
PL/SQL procedure successfully completed.