As you know, the association between an SCN and a timestamp when the SCN is generated is remembered by the database for a limited time period and an error is returned if the SCN specified for the argument to SCN_TO_TIMESTAMP is too old.

Example:

select scn_to_timestamp(max(ora_rowscn)) from MY_TABLE

ORA-08181: el número especificado no es un número de cambio del sistema válido
ORA-06512: en "SYS.SCN_TO_TIMESTAMP", línea 1
08181. 00000 - "specified number is not a valid system change number"
*Cause: supplied scn was beyond the bounds of a valid scn.
*Action: use a valid scn.

Nevertheless, I can obtain the max(ora_rowscn) from MY_TABLE without any kind of error:

select max(ora_rowscn) from MY_TABLE

 MAX(ORA_ROWSCN)
 ---------------
        99464620

I would like to obtain the corresponding timestamp of this ORA_ROWSCN approximately (I don't care if it may vary some hours), without using any AUDIT tool but using PL/SQL statements.

Does exist any relationship between the above MAX(ORA_ROWSCN) from MY_TABLE and the current ORA_ROWSCN from sysdate?

select timestamp_to_scn(sysdate), TO_CHAR(SYSDATE,'dd-mm-yyyy hh24:mi:ss') from dual
 
TIMESTAMP_TO_SCN(SYSDATE)  TO_CHAR(SYSDATE,'dd-mm-yyyy hh24:mi:ss')
-------------------------  ----------------------------------------
         116631465  13-10-2021 12:12:02

Could I calculate, using any kind of algorithm, the corresponding timestamp to 99464620 value?

Thanks in advance.