Assign current_timestamp to timestamp type variable
SQL> SQL> declare 2 t1 timestamp := current_timestamp + 1 ; 3 i1 INTERVAL DAY TO SECOND; 4 begin 5 i1 := t1 - current_timestamp; 6 dbms_output.put_line(i1); 7 end; 8 / +00 23:59:59.789000 PL/SQL procedure successfully completed. SQL> SQL>