Difference between times in JavaScript
<p>I found the following code which is working well for a time sheet calculator I am using</p>

<pre><code>function convertSecondsToHHMMSS(intSecondsToConvert) {
    var hours = convertHours(intSecondsToConvert);
    var minutes = getRemainingMinutes(intSecondsToConvert);
    minutes = (minutes == 60) ? "00" : minutes;
    var seconds = getRemainingSeconds(intSecondsToConvert);
    return hours+" hrs "+minutes+" mins";
}

function convertHours(intSeconds) {
    var minutes = convertMinutes(intSeconds);
    var hours = Math.floor(minutes/60);
    return hours;
}

function convertMinutes(intSeconds) {
    return Math.floor(intSeconds/60);
}

function getRemainingSeconds(intTotalSeconds) {
    return (intTotalSeconds%60);
}

function getRemainingMinutes(intSeconds) {
    var intTotalMinutes = convertMinutes(intSeconds);
    return (intTotalMinutes%60);
}

function HMStoSec1(T) { 
  var A = T.split(/\D+/) ; return (A[0]*60 + +A[1])*60 + +A[2] 
}

var time1 = HMStoSec1("10:00:00");
var time2 = HMStoSec1("12:05:00");
var diff = time2 - time1;
document.write(convertSecondsToHHMMSS(diff));
</code></pre>

<p>It works fine when time1 is greater than time2, if time1 is less than time2 an extra hour is subtracted eg. </p>

<pre><code>var time1 = HMStoSec1("09:00:00");
var time2 = HMStoSec1("08:55:00");
var diff = time2 - time1;
document.write(convertSecondsToHHMMSS(diff)); // writes "1 hr 5 mins" instead of "0 hr 5 mins"
</code></pre>

<p>I think its something to do with the Math.floor in the convertHours function.</p>

<p>I am trying to build something that can just take hours and minutes and subtract/add time, not actually times just quantities of hours and minutes.</p>

<p>There must be a simpler way that sadly eludes me, any help would be greatly appreciated.</p>
