Create table Emp
(
     empno int,
     ename varchar(50),
     doj varchar(30),
     salary int
);

insert into Emp
values (1, 'raj', '2010-06-30 08:10:45', 5000),
       (2, 'kiran', '2018-12-05 18:20:24', 40000),
       (3, 'akbar', '2015-04-12 20:02:45', 9000),
       (4, 'nitin', '2010-03-11 02:10:23', 3000),
       (5, 'Rahul', '2013-12-03 13:23:30', 15000);

-------+------------------+--------------------------+-----------------
empno            ename              doj                      salary
-------+------------------+--------------------------+-----------------
1             raj                2010-06-30 08:10:45         5000
2             kiran              2018-12-05 18:20:24        40000
3             akbar              2015-04-12 20:02:45         9000
4             nitin              2010-03-11 02:10:23         3000
5             Rahul              2013-12-03 13:23:30        15000
-------+------------------+-------------------------+-----------------

select
    format(cast(doj as datetime) - cast('04:00' as datetime), 'yyyy-mm-dd HH:mm:ss') "4Hrs_Minus"
from emp;

-------+-----------------------+---------------------
    empno             doj             4Hrs_Minus
    -------+-----------------------+---------------------
    1         2010-06-30 08:10:45     2010-06-30 04:10:45
    2         2018-12-05 18:20:24     2018-12-05 14:20:24
    3         2015-04-12 20:02:45     2015-04-12 16:02:45
    4         2010-03-11 02:10:23     2010-03-11 22:10:23
    5         2013-12-03 13:23:30     2013-12-03 09:23:30
    -------+-----------------------+----------------------

SELECT empno, doj, date_sub(doj, INTERVAL -4 HOUR) AS 'Adjusted Date' FROM yourtable