From this post:
;WITH CTE AS
WHERE pg_ls_dir <> 'pgsql_tmp'
AND pg_ls_dir::int <= (SELECT relfilenode FROM pg_class WHERE relname ILIKE table_name)
) as folder
,(SELECT relfilenode FROM pg_class WHERE relname ILIKE table_name) filenode
WHERE table_type = 'BASE TABLE'
AND table_schema = 'public'
'./base/' || folder || '/' || filenode
) as creation_time
But, from the comment to this post here, this method is sometimes unreliable. Use at your own risk! You might also be interested in this - it appears that PostgreSQL is finally going down the road of an Oracle wait interface.
If you'd care to file a feature request and post the link in a comment here (with @Vérace in the body), I'd be happy to file a "me-too".