private function sortItemsToDays($items)
    {
        $all = [];

        foreach ($items as $item)
        {
            // date
            $timestamp = strtotime($item->created_at) * 1000;
            $day = Carbon::createFromFormat('Y-m-d H:i:s', $item->created_at)->format('Y-m-d');

            // init empty day
            if (!isset($all[$day])) {
                $all[$day] = [
                    'timestamp' => $timestamp,
                    'date' => $day,
                    'count' => 0,
                ];
            }

            // increase count
            $all[$day]['count']++;
        }

        return $all;
    }