Calculate timespan in JavaScript

Question

I have a .net 2.0 ascx control with a start time and end time textboxes. The data is as follows:

txtStart.Text = 09/19/2008 07:00:00

txtEnd.Text = 09/19/200

Answer 1

I googled for calculating a timespan in javascript and found this question on SO; unfortunately the question text and actual question (only needing hours and minutes) are not the same... so I think I arrived here in error.

I did write an answer to the question title, however - so if anyone else wants something that prints out something like "1 year, and 15 minutes", then this is for you:

function formatTimespan(from, to) {
    var text = '',
        span = { y: 0, m: 0, d: 0, h: 0, n: 0 };

    function calcSpan(n, fnMod) {
        while (from < to) {
            // Modify the date, and check if the from now exceeds the to:
            from = from[fnMod](1);
            if (from <= to) {
                span[n] += 1;
            } else {
                from = from[fnMod](-1);
                return;
            }
        }
    }

    function appendText(n, unit) {
        if (n > 0) {
            text += ((text.length > 0) ? ', ' : '') +
                n.toString(10) + ' ' + unit + ((n === 1) ? '' : 's');
        }
    }

    calcSpan('y', 'addYears');
    calcSpan('m', 'addMonths');
    calcSpan('d', 'addDays');
    calcSpan('h', 'addHours');
    calcSpan('n', 'addMinutes');

    appendText(span.y, 'year');
    appendText(span.m, 'month');
    appendText(span.d, 'day');
    appendText(span.h, 'hour');
    appendText(span.n, 'minute');

    if (text.lastIndexOf(',') < 0) {
        return text;
    }

    return text.substring(0, text.lastIndexOf(',')) + ', and' + text.substring(text.lastIndexOf(',') + 1);
}