CREATE OR REPLACE FUNCTION shift_date_by (date_in      IN DATE,
                                          days_in      IN INTEGER DEFAULT 0,
                                          hours_in     IN INTEGER DEFAULT 0,
                                          minutes_in   IN INTEGER DEFAULT 0,
                                          seconds_in   IN INTEGER DEFAULT 0)
   RETURN DATE
IS
BEGIN
   /* Inspired by @intsiful
      http://bkintsiful.blogspot.com/2012/04/how-does-one-add-dayhourminutesecond-to.html */
   RETURN   date_in
          + days_in
          + (hours_in / 24)
          + (minutes_in / 1440)
          + (seconds_in / 86400);
END;

DECLARE 
   c_start   DATE := TO_DATE ('2016-10-12 15:15:15', 'YYYY-MM-DD HH24:MI:SS'); 
 
   PROCEDURE show_date (date_in IN DATE) 
   IS 
   BEGIN 
      DBMS_OUTPUT.put_line (TO_CHAR (date_in, 'YYYY-MM-DD HH24:MI:SS')); 
   END; 
BEGIN 
   show_date (shift_date_by (c_start, 1)); 
   show_date (shift_date_by (c_start, -1)); 
   show_date (shift_date_by (c_start, 0, 1)); 
   show_date (shift_date_by (c_start, 0, -1)); 
   show_date (shift_date_by (c_start, 
                             0, 
                             0, 
                             10)); 
   show_date (shift_date_by (c_start, 
                             0, 
                             0, 
                             -10)); 
   show_date (shift_date_by (c_start, 
                             0, 
                             0, 
                             0, 
                             10)); 
   show_date (shift_date_by (c_start, 
                             0, 
                             0, 
                             0, 
                             -10)); 
END;