Because my date ends with ".000000Z"

I'm having trouble displaying the notification date correctly.

In the laravel notification table, the date is stored correctly like this: 2020-09-14 15:28:21

But when I get this date for display, it is returned like this: created_at: "2020-09-14T15: 28: 21.000000Z"

So my date appears correct on the display, but the time is never the same.

I'm doing this to capture notifications:

$notifications = $request->user()->notifications()
        ->limit(7)
        ->get()
        ->each(function ($notification) {
            $notification->formatted_created_at = $notification->created_at->format(__('notifications.dateformat'));
      });

And I get this:

0:
created_at: "2020-09-14T15:28:21.000000Z"
data: Object
formatted_created_at: "14/09/2020 03:09:21"
id: (...)
notifiable_id: (...)
notifiable_type: (...)
read_at: (...)
type: (...)
updated_at: (...)

Formatted_created_at doesn't seem to be forming the date correctly due to this strange format in created_at (but the database is correct).

That is, when it comes to listing the notifications, the date appears correct, but the time always returns 03:09 and only the seconds vary, that is:

03:09:08 | 03:09:31 | 03:09:54 ...

What is happening ?