Datetime-local keeps backing to old value when I change it to new in jquery

Greetings I have a problem with my code and I don't know why is doing that when I load my page a have some dummy value for my datetime-local but when I change it keeps"bouncing" from old to new value here is the code and screenshot of example

enter image description here

enter image description here

enter image description here

var timer = 'Apr 29, 2029 00:00:00';
                var newTimer = '';
                countDown(new Date(timer));

            $("#dateandtime").change(function(){
                if($("#dateandtime").val() != ""){
                    var time = $("#dateandtime").val();
                    var dealTimer = new Date(time);
                    newTimer += dealTimer;
                }

                countDown(new Date(!newTimer ? timer: newTimer));
            });
How many English words
do you know?
Test your English vocabulary size, and measure
how many words do you know
Online Test
Powered by Examplum