public static function concat($startingDate, $endingDate)
    {
        $startingDateArray = explode('-', $startingDate);
        $endingDateArray = explode('-', $endingDate);
        $endingDateFormat = '%A %d %B %Y';

        if ($startingDate == $endingDate) {
            $startingDateFormat = '%A %d %B %Y';

            return Carbon::createFromFormat('Y-m-d', $startingDate)->formatLocalized($startingDateFormat);
        }

        if ($startingDateArray[1] == $endingDateArray[1]) {
            // mois égaux
            $startingDateFormat = '%A %d';
        } elseif ($startingDateArray[0] == $endingDateArray[0]) {
            // annee égales
            $startingDateFormat = '%A %d %B';
        } else {
            $startingDateFormat = '%A %d %B %Y';
        }

        return Carbon::createFromFormat('Y-m-d', $startingDate)
            ->formatLocalized($startingDateFormat).' to '.Carbon::createFromFormat('Y-m-d', $endingDate)
            ->formatLocalized($endingDateFormat);
    }