Oracle 18c

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Select to_char(to_date(floor(2455198), 'J') + mod(2455197, 1) + 0.5, 'DD-MM-YYYY HH24:mi:ss') from dual;

TO_CHAR(TO_DATE(FLOOR(2455198),'J')+MOD(2455197,1)+0.5,'DD-MM-YYYYHH24:MI:SS')

01-01-2010 12:00:00

Select to_char(to_date(floor(2455197.75001), 'J') + mod(2455197.75001, 1) + 0.5, 'DD-MM-YYYY HH24:mi:ss') from dual;

TO_CHAR(TO_DATE(FLOOR(2455197.75001),'J')+MOD(2455197.75001,1)+0.5,'DD-MM-YYYYHH24:MI:SS')

01-01-2010 06:00:01

Select to_char(to_date(floor(2456293.520833), 'J') + mod(2456293.520833, 1) + 0.5, 'DD-MM-YYYY HH24:mi:ss') from dual;

TO_CHAR(TO_DATE(FLOOR(2456293.520833),'J')+MOD(2456293.520833,1)+0.5,'DD-MM-YYYYHH24:MI:SS')

01-01-2013 00:30:00