public function setCreatedAtAttribute($createdAt)
    {
        if (!$createdAt) {
            return;
        }

        if (!$createdAt instanceof DateTime) {
            $createdAt = Carbon::parse($createdAt);
        }

        $timestamp = $createdAt->format('U');
        $timestamp = 30 * round($timestamp / 30);

        $date = Carbon::createFromFormat('U', $timestamp)->toDateTimeString();

        $this->attributes['created_at'] = $date;

        return $date;
    }