Default date format in Oracle is DD-MON-RR (25-JAN-18). With that output, we can't using date formatting.

Too solve this issue, we must change date format oracle like date commonly using

ALTER SESSION SET NLS_DATE_FORMAT = ...

Add this script inside your database connection file

<?php

return [
    'class' => 'yii\db\Connection',
    'dsn' => 'oci:host=127.0.0.1:1521/XE',
    'username' => 'your_username',
    'password' => 'your_password',
    'charset' => 'utf8',

    // Schema cache options (for production environment)
    //'enableSchemaCache' => true,
    //'schemaCacheDuration' => 60,
    //'schemaCache' => 'cache',

    'on afterOpen' => function($event) {
        // $event->sender refers to the DB connection
        $event->sender->createCommand("ALTER SESSION SET NLS_DATE_FORMAT='DD-MM-YYYY hh24:mi:ss'")->execute();
    }    
];