Oracle 18c

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create table t as
    select '01-jun-2021' as start_date, '02-jun-2021' as end_date, '08:00' as start_time, '10:00' as end_time, 30 as interval from dual union all
    select '03-jun-2021' as start_date, '04-jun-2021' as end_date, '10:00' as start_time, '12:00' as end_time, 15 as interval from dual 
2 rows affected

with cte (start_date, end_date, interval) as (
      select to_date(start_date||start_time, 'DD-Mon-YYYYHH24:MI'), to_date(end_date||end_time, 'DD-Mon-YYYYHH24:MI'), interval
      from t
      union all
      select cte.start_date + cte.interval * interval '1' minute, end_date, interval
      from cte
      where cte.start_date < end_date
     )
select cast(start_date as timestamp)
from cte
order by start_date

CAST(START_DATEASTIMESTAMP)

01-JUN-21 08.00.00.000000

01-JUN-21 08.30.00.000000

01-JUN-21 09.00.00.000000

01-JUN-21 09.30.00.000000

01-JUN-21 10.00.00.000000

01-JUN-21 10.30.00.000000

01-JUN-21 11.00.00.000000

01-JUN-21 11.30.00.000000

01-JUN-21 12.00.00.000000

01-JUN-21 12.30.00.000000

01-JUN-21 13.00.00.000000

01-JUN-21 13.30.00.000000

01-JUN-21 14.00.00.000000

01-JUN-21 14.30.00.000000

01-JUN-21 15.00.00.000000

01-JUN-21 15.30.00.000000

01-JUN-21 16.00.00.000000

01-JUN-21 16.30.00.000000

01-JUN-21 17.00.00.000000

01-JUN-21 17.30.00.000000

01-JUN-21 18.00.00.000000

01-JUN-21 18.30.00.000000

01-JUN-21 19.00.00.000000

01-JUN-21 19.30.00.000000

01-JUN-21 20.00.00.000000

01-JUN-21 20.30.00.000000

01-JUN-21 21.00.00.000000

01-JUN-21 21.30.00.000000

01-JUN-21 22.00.00.000000

01-JUN-21 22.30.00.000000

01-JUN-21 23.00.00.000000

01-JUN-21 23.30.00.000000

02-JUN-21 00.00.00.000000

02-JUN-21 00.30.00.000000

02-JUN-21 01.00.00.000000

02-JUN-21 01.30.00.000000

02-JUN-21 02.00.00.000000

02-JUN-21 02.30.00.000000

02-JUN-21 03.00.00.000000

02-JUN-21 03.30.00.000000

02-JUN-21 04.00.00.000000

02-JUN-21 04.30.00.000000

02-JUN-21 05.00.00.000000

02-JUN-21 05.30.00.000000

02-JUN-21 06.00.00.000000

02-JUN-21 06.30.00.000000

02-JUN-21 07.00.00.000000

02-JUN-21 07.30.00.000000

02-JUN-21 08.00.00.000000

02-JUN-21 08.30.00.000000

02-JUN-21 09.00.00.000000

02-JUN-21 09.30.00.000000

02-JUN-21 10.00.00.000000

03-JUN-21 10.00.00.000000

03-JUN-21 10.15.00.000000

03-JUN-21 10.30.00.000000

03-JUN-21 10.45.00.000000

03-JUN-21 11.00.00.000000

03-JUN-21 11.15.00.000000

03-JUN-21 11.30.00.000000

03-JUN-21 11.45.00.000000

03-JUN-21 12.00.00.000000

03-JUN-21 12.15.00.000000

03-JUN-21 12.30.00.000000

03-JUN-21 12.45.00.000000

03-JUN-21 13.00.00.000000

03-JUN-21 13.15.00.000000

03-JUN-21 13.30.00.000000

03-JUN-21 13.45.00.000000

03-JUN-21 14.00.00.000000

03-JUN-21 14.15.00.000000

03-JUN-21 14.30.00.000000

03-JUN-21 14.45.00.000000

03-JUN-21 15.00.00.000000

03-JUN-21 15.15.00.000000

03-JUN-21 15.30.00.000000

03-JUN-21 15.45.00.000000

03-JUN-21 16.00.00.000000

03-JUN-21 16.15.00.000000

03-JUN-21 16.30.00.000000

03-JUN-21 16.45.00.000000

03-JUN-21 17.00.00.000000

03-JUN-21 17.15.00.000000

03-JUN-21 17.30.00.000000

03-JUN-21 17.45.00.000000

03-JUN-21 18.00.00.000000

03-JUN-21 18.15.00.000000

03-JUN-21 18.30.00.000000

03-JUN-21 18.45.00.000000

03-JUN-21 19.00.00.000000

03-JUN-21 19.15.00.000000

03-JUN-21 19.30.00.000000

03-JUN-21 19.45.00.000000

03-JUN-21 20.00.00.000000

03-JUN-21 20.15.00.000000

03-JUN-21 20.30.00.000000

03-JUN-21 20.45.00.000000

03-JUN-21 21.00.00.000000

03-JUN-21 21.15.00.000000

03-JUN-21 21.30.00.000000

03-JUN-21 21.45.00.000000

03-JUN-21 22.00.00.000000

03-JUN-21 22.15.00.000000

03-JUN-21 22.30.00.000000

03-JUN-21 22.45.00.000000

03-JUN-21 23.00.00.000000

03-JUN-21 23.15.00.000000

03-JUN-21 23.30.00.000000

03-JUN-21 23.45.00.000000

04-JUN-21 00.00.00.000000

04-JUN-21 00.15.00.000000

04-JUN-21 00.30.00.000000

04-JUN-21 00.45.00.000000

04-JUN-21 01.00.00.000000

04-JUN-21 01.15.00.000000

04-JUN-21 01.30.00.000000

04-JUN-21 01.45.00.000000

04-JUN-21 02.00.00.000000

04-JUN-21 02.15.00.000000

04-JUN-21 02.30.00.000000

04-JUN-21 02.45.00.000000

04-JUN-21 03.00.00.000000

04-JUN-21 03.15.00.000000

04-JUN-21 03.30.00.000000

04-JUN-21 03.45.00.000000

04-JUN-21 04.00.00.000000

04-JUN-21 04.15.00.000000

04-JUN-21 04.30.00.000000

04-JUN-21 04.45.00.000000

04-JUN-21 05.00.00.000000

04-JUN-21 05.15.00.000000

04-JUN-21 05.30.00.000000

04-JUN-21 05.45.00.000000

04-JUN-21 06.00.00.000000

04-JUN-21 06.15.00.000000

04-JUN-21 06.30.00.000000

04-JUN-21 06.45.00.000000

04-JUN-21 07.00.00.000000

04-JUN-21 07.15.00.000000

04-JUN-21 07.30.00.000000

04-JUN-21 07.45.00.000000

04-JUN-21 08.00.00.000000

04-JUN-21 08.15.00.000000

04-JUN-21 08.30.00.000000

04-JUN-21 08.45.00.000000

04-JUN-21 09.00.00.000000

04-JUN-21 09.15.00.000000

04-JUN-21 09.30.00.000000

04-JUN-21 09.45.00.000000

04-JUN-21 10.00.00.000000

04-JUN-21 10.15.00.000000

04-JUN-21 10.30.00.000000

04-JUN-21 10.45.00.000000

04-JUN-21 11.00.00.000000

04-JUN-21 11.15.00.000000

04-JUN-21 11.30.00.000000

04-JUN-21 11.45.00.000000

04-JUN-21 12.00.00.000000

      select to_date(start_date||start_time, 'DD-Mon-YYYYHH24:MI'), to_date(end_date||end_time, 'DD-Mon-YYYYHH24:MI'), interval
      from t

TO_DATE(START_DATE||START_TIME,'DD-MON-YYYYHH24:MI')
TO_DATE(END_DATE||END_TIME,'DD-MON-YYYYHH24:MI')
INTERVAL

01-JUN-21
02-JUN-21
30

03-JUN-21
04-JUN-21
15