Oracle 18c

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
CREATE TABLE table_name (
  event_time_1 varchar2(10),
  event_time_2 varchar2(10)
);
INSERT INTO table_name (event_time_1, event_time_2)
SELECT '10:01', '10:04' FROM DUAL UNION ALL
SELECT '10:02', '10:06' FROM DUAL
2 rows affected

SELECT event_time_1,
       event_time_2,
       (
         TO_DATE(event_time_2, 'HH24:MI')
         - TO_DATE(event_time_1, 'HH24:MI')
       ) DAY TO SECOND AS interval_diff,
       (
         TO_DATE(event_time_2, 'HH24:MI')
         - TO_DATE(event_time_1, 'HH24:MI')
       ) AS days_diff,
       (
         TO_DATE(event_time_2, 'HH24:MI')
         - TO_DATE(event_time_1, 'HH24:MI')
       ) * 24 * 60 AS minutes_diff
FROM   table_name


EVENT_TIME_1
EVENT_TIME_2
INTERVAL_DIFF
DAYS_DIFF
MINUTES_DIFF


10:01
10:04
+00 00:03:00.000000
.002083333333333333333333333333333333333333
3

10:02
10:06
+00 00:04:00.000000
.002777777777777777777777777777777777777778
4

EVENT_TIME_1	EVENT_TIME_2	INTERVAL_DIFF	DAYS_DIFF	MINUTES_DIFF
10:01	10:04	+00 00:03:00.000000	.002083333333333333333333333333333333333333	3
10:02	10:06	+00 00:04:00.000000	.002777777777777777777777777777777777777778	4