Change jQuery input date to SQLdate to be used in Ajax call

Im struggling to match the date value in the MySQL server with the jquery UI input date

This is what i have tried

$('#start_date').datepicker({dateFormat:'dd-mm-yy'});

ajax call

$(document).on('change', '#hotelid', function() {
    
      var hotid = $('#hotelid').val();
      
      onHotelIdUpdate(hotid);
    });
    function onHotelIdUpdate(val) {
         var bookdate = $('#start_date').val();
         
    console.log('onHotelIdUpdate() called with the val: ', val);
         $.ajax({
         type:'get',
         url: "{{ route('hotel.rate') }}",
         data:{     
               '_token':$('input[name=_token]').val(),
               'hotelid': val, 
                'bookdate': bookdate            
               }, 
               
             success:function(data){
            console.log(data);
            $("#avail").val(data.rooms);
                },
            error: function(){
           console.log("Error Occurred");
                 }

my controller function in laravel

public function getRates(Request $request )
    {
           $hotelid = $request->input('hotelid');
           $date = $request->input('bookdate');
           $rates=hotelroom::where('hotel_id',$hotelid)
                       ->where('available_date',$date)
                       ->first();                 
                           
           return response()->json($rates);
      
     }

This works fine without the "bookdate" variable im sending but when i include it returns blank record i have also notices in the input checkbox the date is showing as " dd-mm-yyyy' but in the database the date value im trying to match has the date as " yyyy-mm-dd" how to fix this ?