Oracle 21c

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ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
declare
    s varchar2(100) := '2023-02-24 14:22:49';       
    f varchar2(100) := null;
    f1 varchar2(100) := 'yyyy-mm-dd hh24:mi:ss';
    f2 varchar2(100) := 'dd/mm/yyyy hh24:mi:ss';
    d date := null;
begin
    f := f1;
    d := to_date(s,f);
    dbms_output.put_line(f||' --> '||d);
    f := f2;
    d := to_date(s,f);
    dbms_output.put_line(f||' --> '||d);
exception
    when others then
        dbms_output.put_line(s||' --> '||f||' >>>> '||sqlerrm);
end;
/
1 rows affected

dbms_output:
yyyy-mm-dd hh24:mi:ss --> 2023-02-24 14:22:49
2023-02-24 14:22:49 --> dd/mm/yyyy hh24:mi:ss >>>> ORA-01861: literal does not match format string

declare
    s varchar2(100) := '05/03/2023 08:44';
    f varchar2(100) := null;
    f1 varchar2(100) := 'yyyy-mm-dd hh24:mi:ss';
    f2 varchar2(100) := 'dd/mm/yyyy hh24:mi:ss';
    d date := null;
begin
    f := f1;
    d := to_date(s,f);
    dbms_output.put_line(f||' --> '||d);
    f := f2;
    d := to_date(s,f);
    dbms_output.put_line(f||' --> '||d);
exception
    when others then
        dbms_output.put_line(s||' --> '||f||' >>>> '||sqlerrm);
end;
/
1 rows affected

dbms_output:
yyyy-mm-dd hh24:mi:ss --> 0005-03-20 23:08:44
dd/mm/yyyy hh24:mi:ss --> 2023-03-05 08:44:00

declare
    s varchar2(100) := '05/03/2023 08:44';
    f varchar2(100) := null;
    f1 varchar2(100) := 'fxyyyy-mm-dd hh24:mi:ss';
    f2 varchar2(100) := 'fxdd/mm/yyyy hh24:mi:ss';
    d date := null;
begin
    f := f1;
    d := to_date(s,f);
    dbms_output.put_line(f||' --> '||d);
    f := f2;
    d := to_date(s,f);
    dbms_output.put_line(f||' --> '||d);
exception
    when others then
        dbms_output.put_line(s||' --> '||f||' >>>> '||sqlerrm);
end;
/
1 rows affected

dbms_output:
05/03/2023 08:44 --> fxyyyy-mm-dd hh24:mi:ss >>>> ORA-01862: the numeric value does not match the length of the format item