JSFiddle - React, Tailwind, and code Playground

HTML

<input id="first" value="1/1/2000"/>
<input id="second" value="1/1/2001"/>
<input id="abc" value=""/>

JavaScript

function parseDate(str) {
    var mdy = str.split('/')
    return new Date(mdy[2], mdy[0]-1, mdy[1]);
}
function daydiff(first, second) {
    return (second-first)/(1000*60*60*24)
}
var newVal = (daydiff(parseDate($('#first').val()), parseDate($('#second').val())));    
$('#abc').val(newVal);

    
$(document).ready(function() {    
if (newVal <= '365') {
    $('#abc').fadeOut('slow');       
    }
else if (newVal == '365') {
    $('#abc').fadeOut('slow');       
    }
else if (newVal >= '366') {
     $('#abc').fadeOut('slow');       
     }
});