Alright, it’s clearer now, but I don’t know if you can change that in the UI.
Looking at the database structure and at that link it could be storage_mtime.
storage_mtime int The last modified date of the file as a UNIX timestamp as stored on the storage.
mysql> describe oc_filecache;
+------------------+---------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------------+---------------+------+-----+---------+----------------+
| fileid | bigint(20) | NO | PRI | NULL | auto_increment |
| storage | int(11) | NO | MUL | 0 | |
| path | varchar(4000) | YES | | NULL | |
| path_hash | varchar(32) | NO | | | |
| parent | bigint(20) | NO | MUL | 0 | |
| name | varchar(250) | YES | | NULL | |
| mimetype | int(11) | NO | | 0 | |
| mimepart | int(11) | NO | | 0 | |
| size | bigint(20) | NO | | 0 | |
| mtime | bigint(20) | NO | | 0 | |
| storage_mtime | bigint(20) | NO | | 0 | |
| encrypted | int(11) | NO | | 0 | |
| unencrypted_size | bigint(20) | NO | | 0 | |
| etag | varchar(40) | YES | | NULL | |
| permissions | int(11) | YES | | 0 | |
| checksum | varchar(255) | YES | | NULL | |
+------------------+---------------+------+-----+---------+----------------+
16 rows in set (0.00 sec)
Nevertheless fyi if you have the activity app and click on a file, you’ll have the history of modifications, and also the creation time.