Как объединить массивы дат?

public function add(Days $days): Days 
    { 
 
         
    }

class Days 
{ 
    private $rangeDays; 
 
    public function __construct(array $rangeDays) 
    { 
        $this->rangeDays = $rangeDays; 
    } 
 
    public function remove(array $arr): Days 
    { 
 
        return new Days(array_diff($this->rangeDays, $arr)); 
    } 
 
    public function add(Days $days): Days 
    { 
 
        
    } 
 
    public static function fromRange($startDate, $endDate) 
    { 
        $vacationsDate = []; 
 
        $start = new Carbon($startDate->format('Y-m-d')); 
        $end = new Carbon($endDate->format('Y-m-d')); 
 
        while ($start->lte($end)) { 
            $vacationsDate[] = $start->toDateString(); 
            $start->addDay(); 
        } 
 
        return new self($vacationsDate); 
    } 
 
 
}