yii2 – 如何在数据库中添加当前时间戳.格式是什么？

use yii\behaviors\TimestampBehavior;
use yii\db\Expression;

public function behaviors()
{
    return [
        // Other behaviors
        [
            'class' => TimestampBehavior::className(),'createdAtAttribute' => 'time_created','updatedAtAttribute' => false,'value' => new Expression('Now()'),],];   
}