How to calculate date difference in JavaScript?

Question

I want to calculate date difference in days, hours, minutes, seconds, milliseconds, nanoseconds. How can I do it?

Answer 1

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("
Number of days since "+dString+": "+DateDiff.inDays(d1, d2));
document.write("
Number of weeks since "+dString+": "+DateDiff.inWeeks(d1, d2));
document.write("
Number of months since "+dString+": "+DateDiff.inMonths(d1, d2));
document.write("
Number of years since "+dString+": "+DateDiff.inYears(d1, d2));

Code sample taken from here.