The timestamps will be Carbon instances; you can use the toDateString method to display the Y-m-d H:i:s format. If you override the toArray method on the Model; you can specify how the timestamps should be serialized:
public function toArray()
{
return array_merge(parent::toArray(), [
'created_at' => $this->created_at->toDateTimeString(),
'updated_at' => $this->updated_at->toDateTimeString(),
]);
}
Or, you can cast the created_at and updated_at timestamps with defined formats:
protected $casts = [
'created_at' => 'datetime:Y-m-d H:i:s',
'updated_at' => 'datetime:Y-m-d H:i:s',
];