Note: You can look OID of the table from pg_class and the do ls -l in the greenplum data directory to find table creation date.

sachi=# select oid,* from pg_class where relname ='abctest';
oid | relname | relnamespace | reltype | relowner | relam | relfilenode | reltablespace | relpages | reltuples | reltoastrelid | reltoastidxid | relaoseg
relid | relaosegidxid | relhasindex | relisshared | relkind | relstorage | relnatts | relchecks | reltriggers | relukeys | relfkeys | relrefs | relhasoids |
relhaspkey | relhasrules | relhassubclass | relfrozenxid | relacl | reloptions
--------+---------+--------------+---------+----------+-------+-------------+---------------+----------+-----------+---------------+---------------+---------
------+---------------+-------------+-------------+---------+------------+----------+-----------+-------------+----------+----------+---------+------------+-
-----------+-------------+----------------+--------------+--------+------------
113641 | abctest | 2200 | 113642 | 10 | 0 | 113641 | 0 | 1 | 3 | 0 | 0 |
0 | 0 | f | f | r | h | 1 | 0 | 0 | 0 | 0 | 0 | f |
f | f | f | 619248 | |
(1 row)
sachi=# 
[gpadmin@sachi base]$ find . -name 113641
./16993/113641
[gpadmin@sachi base]$ ls -l ./16993/113641
-rw-------. 1 gpadmin gpadmin 32768 Nov 10 13:32 ./16993/113641
[gpadmin@sachi base]$