Database Creation Date
A simple way that can check the creation date of a database. When the data is running, no matter the instance is open or mounted, we can query the database.
First of all, we format the date time of current session.
[oracle@primary01 ~]$ sqlplus / as sysdba
...
SQL> alter session set nls_date_format='YYYY-MM-DD HH24:MI:SS';
Session altered.
Then we perform the query.
SQL> select name, created from v$database;
NAME CREATED
--------- -------------------
ORCLCDB 2020-11-28 21:10:53
The result shows the creation data of the database.
Pluggable Database Creation Date
For pluggable databases (PDB), you have to specify the PDB name for checking its creation date by querying V$PDBS:
SQL> select creation_time from v$pdbs where name = 'ORCLPDB2';
CREATION_TIME
-------------------
2021-01-12 19:30:55
To know the startup time of a database, we need more thinking.