Moment.js - two dates difference in number of days

From the moment.js docs: format('E') stands for day of week. thus your diff is being computed on which day of the week, which has to be between 1 and 7.

From the moment.js docs again, here is what they suggest:

var a = moment([2007, 0, 29]);
var b = moment([2007, 0, 28]);
a.diff(b, 'days') // 1

Here is a JSFiddle for your particular case:

$('#test').click(function() {
  var startDate = moment("13.04.2016", "DD.MM.YYYY");
  var endDate = moment("28.04.2016", "DD.MM.YYYY");

  var result = 'Diff: ' + endDate.diff(startDate, 'days');

  $('#result').html(result);
});

#test {
  width: 100px;
  height: 100px;
  background: #ffb;
  padding: 10px;
  border: 2px solid #999;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.12.0/moment.js"></script>

<div id='test'>Click Me!!!</div>
<div id='result'></div>

Here's how you can get the comprehensive full fledge difference of two dates.

 function diffYMDHMS(date1, date2) {

    let years = date1.diff(date2, 'year');
    date2.add(years, 'years');

    let months = date1.diff(date2, 'months');
    date2.add(months, 'months');

    let days = date1.diff(date2, 'days');
    date2.add(days, 'days');

    let hours = date1.diff(date2, 'hours');
    date2.add(hours, 'hours');

    let minutes = date1.diff(date2, 'minutes');
    date2.add(minutes, 'minutes');

    let seconds = date1.diff(date2, 'seconds');

    console.log(years + ' years ' + months + ' months ' + days + ' days ' + hours + ' 
    hours ' + minutes + ' minutes ' + seconds + ' seconds'); 

    return { years, months, days, hours, minutes, seconds};
}

Use moment.js to find the difference between two dates in days.

Install moment.js using the following command,

npm install moment

Calculate the difference between two dates in days.

var moment = require('moment');

var date1 = moment("2022-10-30");
var date2 = moment("2022-12-30");
var days = date1.diff(date2, 'days')