[javascript] How to calculate number of days between two dates

I have two input dates taking from Date Picker control. I have selected start date 2/2/2012 and end date 2/7/2012. I have written following code for that.

I should get result as 6 but I am getting 5.

function SetDays(invoker) {   
    var start = $find('<%=StartWebDatePicker.ClientID%>').get_value();
    var end = $find('<%=EndWebDatePicker.ClientID%>').get_value();

    var oneDay=1000 * 60 * 60 * 24;
    var difference_ms = Math.abs(end.getTime() - start.getTime())
    var diffValue = Math.round(difference_ms / oneDay);
}

Can anyone tell me how I can get exact difference?

MVC i have two input text 1: number of day 2: datetime picker

 @Html.TextBox("HeaderINVID", null, new { @id = "HeaderINVID", @type = "number", @class = "form-control", autocomplete = "off", placeholder = "Day Count " })

  @Html.TextBox("HeaderINVDT", null, new { id = "HeaderINVDT", @class = "form-control format-picker", autocomplete = "off", placeholder = " Date" })

javascipt

to calculate number from date use

    $("#HeaderINVID").bind("keyup", function (e) {
        var INVID = $("#HeaderINVID").val();
        var date = moment()
            .add(INVID, 'd')
            .toDate(); 
        $("#HeaderINVDT").val(moment(date).format('YYYY-MM-DD')) ;
    })

to calculate number of days between two dates use

  $("#HeaderINVDT").bind('change', function (e) {
        var StDT = moment($("#HeaderINVDT").val()).startOf('day');
        var NODT = moment().startOf('day');
        $("#HeaderINVID").val(StDT.diff(NODT, 'days'));
    })

do not forget to add http://momentjs.com/

I made a quick re-usable function in ES6 using Moment.js.

const getDaysDiff = (start_date, end_date, date_format = 'YYYY-MM-DD') => {_x000D_
  const getDateAsArray = (date) => {_x000D_
    return moment(date.split(/\D+/), date_format);_x000D_
  }_x000D_
  return getDateAsArray(end_date).diff(getDateAsArray(start_date), 'days') + 1;_x000D_
}_x000D_
_x000D_
console.log(getDaysDiff('2019-10-01', '2019-10-30'));_x000D_
console.log(getDaysDiff('2019/10/01', '2019/10/30'));_x000D_
console.log(getDaysDiff('2019.10-01', '2019.10 30'));_x000D_
console.log(getDaysDiff('2019 10 01', '2019 10 30'));_x000D_
console.log(getDaysDiff('+++++2019!!/###10/$$01', '2019-10-30'));_x000D_
console.log(getDaysDiff('2019-10-01-2019', '2019-10-30'));_x000D_
console.log(getDaysDiff('10-01-2019', '10-30-2019', 'MM-DD-YYYY'));_x000D_
_x000D_
console.log(getDaysDiff('10-01-2019', '10-30-2019'));_x000D_
console.log(getDaysDiff('10-01-2019', '2019-10-30', 'MM-DD-YYYY'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.24.0/moment.js"></script>

This works for me:

const from = '2019-01-01';_x000D_
const to   = '2019-01-08';_x000D_
_x000D_
Math.abs(_x000D_
    moment(from, 'YYYY-MM-DD')_x000D_
      .startOf('day')_x000D_
      .diff(moment(to, 'YYYY-MM-DD').startOf('day'), 'days')_x000D_
  ) + 1_x000D_
);

If you are using moment.js you can do it easily.

var start = moment("2018-03-10", "YYYY-MM-DD");
var end = moment("2018-03-15", "YYYY-MM-DD");

//Difference in number of days
moment.duration(start.diff(end)).asDays();

//Difference in number of weeks
moment.duration(start.diff(end)).asWeeks();

If you want to find difference between a given date and current date in number of days (ignoring time), make sure to remove time from moment object of current date as below

moment().startOf('day')

To find difference between a given date and current date in number of days

var given = moment("2018-03-10", "YYYY-MM-DD");
var current = moment().startOf('day');

//Difference in number of days
moment.duration(given.diff(current)).asDays();

Try:

//Difference in days

var diff =  Math.floor(( start - end ) / 86400000);
alert(diff);

Try this Using moment.js (Its quite easy to compute date operations in javascript)

firstDate.diff(secondDate, 'days', false);// true|false for fraction value

Result will give you number of days in integer.

Also you can use this code: moment("yourDateHere", "YYYY-MM-DD").fromNow(). This will calculate the difference between today and your provided date.