How to calculate the total days between two selected calendar dates

Question

Let say i have startDate = 7/16/2015 and endDate = 7/20/2015. This 2 dates are stored in a SharePoint list.

If user select the exact date with the date in SharePoint list, it can calculate the total days = 2 , which means that without calculate on the other days.

Anyone can please help on this?

I use the following code to calculate the total day of difference without counting on weekend. But I cant figure out the way how to calculate the total day of selected date without counting on other days.

function workingDaysBetweenDates(startDate,endDate) {

// Validate input
if (endDate < startDate)
    return 'Invalid !';

// Calculate days between dates
var millisecondsPerDay = 86400 * 1000; // Day in milliseconds
startDate.setHours(0,0,0,1);  // Start just after midnight
endDate.setHours(23,59,59,999);  // End just before midnight
var diff = endDate - startDate;  // Milliseconds between datetime objects    
var days = Math.ceil(diff / millisecondsPerDay);

// Subtract two weekend days for every week in between
var weeks = Math.floor(days / 7);
var days = days - (weeks * 2);

// Handle special cases
var startDay = startDate.getDay();
var endDay = endDate.getDay();

// Remove weekend not previously removed.   
if (startDay - endDay > 1)         
    days = days - 2;


// Remove start day if span starts on Sunday but ends before Saturday
if (startDay == 0 && endDay != 6)
    days = days - 1; 

// Remove end day if span ends on Saturday but starts after Sunday
if (endDay == 6 && startDay != 0)
    days = days - 1;

return days;

}

Answer 1

The following function calculates the number of business days between two dates

function getBusinessDatesCount(startDate, endDate) {
    var count = 0;
    var curDate = startDate;
    while (curDate <= endDate) {
        var dayOfWeek = curDate.getDay();
        if(!((dayOfWeek == 6) || (dayOfWeek == 0)))
           count++;
        curDate.setDate(curDate.getDate() + 1);
    }
    return count;
}


//Usage

var startDate = new Date('7/16/2015');
var endDate = new Date('7/20/2015');
var numOfDates = getBusinessDatesCount(startDate,endDate);
$('div#result').text(numOfDates);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="result"/>

Answer 2

First you have to calculate the difference in time, then convert the time to days

var calculateDifference = function(date1, date2){
    var timeDifference = Math.abs(date2.getTime() - date1.getTime());
    return Math.ceil(timeDifference / (1000 * 3600 * 24));//ms * seconds * hours
}

var difference = calculateDifference(new Date("7/16/2015"), new Date("7/20/2015"));

untested, but should work...