How to calculate date difference in JavaScript?

Assuming you have two Date objects, you can just subtract them to get the difference in milliseconds:

var difference = date2 - date1;

From there, you can use simple arithmetic to derive the other values.

var DateDiff = {    inDays: function(d1, d2) {        var t2 = d2.getTime();        var t1 = d1.getTime();        return parseInt((t2-t1)/(24*3600*1000));    },    inWeeks: function(d1, d2) {        var t2 = d2.getTime();        var t1 = d1.getTime();        return parseInt((t2-t1)/(24*3600*1000*7));    },    inMonths: function(d1, d2) {        var d1Y = d1.getFullYear();        var d2Y = d2.getFullYear();        var d1M = d1.getMonth();        var d2M = d2.getMonth();        return (d2M+12*d2Y)-(d1M+12*d1Y);    },    inYears: function(d1, d2) {        return d2.getFullYear()-d1.getFullYear();    }}var dString = "May, 20, 1984";var d1 = new Date(dString);var d2 = new Date();document.write("<br />Number of <b>days</b> since "+dString+": "+DateDiff.inDays(d1, d2));document.write("<br />Number of <b>weeks</b> since "+dString+": "+DateDiff.inWeeks(d1, d2));document.write("<br />Number of <b>months</b> since "+dString+": "+DateDiff.inMonths(d1, d2));document.write("<br />Number of <b>years</b> since "+dString+": "+DateDiff.inYears(d1, d2));

Code sample taken from here.

Another solution is convert difference to a new Date object and get that date's year(diff from 1970), month, day etc.

var date1 = new Date(2010, 6, 17);var date2 = new Date(2013, 12, 18);var diff = new Date(date2.getTime() - date1.getTime());// diff is: Thu Jul 05 1973 04:00:00 GMT+0300 (EEST)console.log(diff.getUTCFullYear() - 1970); // Gives difference as year// 3console.log(diff.getUTCMonth()); // Gives month count of difference// 6console.log(diff.getUTCDate() - 1); // Gives day count of difference// 4

So difference is like "3 years and 6 months and 4 days". If you want to take difference in a human readable style, that can help you.