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How to convert Seconds to Time in Javascript

I have to convert seconds to time format:
seconds_1 = 540;
seconds_2 = -2820;
convert_1 = new Date(seconds_1 * 1000).toISOString().substr(11, 8);
convert_2 = new Date(seconds_2 * 1000).toISOString().substr(11, 8);
console.log(convert_1);
console.log(convert_2);
it will return,
convert_1 : 00:09:00
convert_2 : 23:13:00
first one (convert_1) is correct, but the second one should return -00:47:00 .
The Actual issue is, the negative value is not converting to time correctly.
Please help.
I tried this,
function toTime(duration) {
// Hours, minutes and seconds
var hrs = ~~(duration / 3600);
var mins = ~~((duration % 3600) / 60);
var secs = ~~duration % 60;
let ret = hrs+ ":" + mins + ":" + secs;
return ret;
}
seconds_1 = 540;
seconds_2 = -2820;
console.log(toTime(seconds_2 ));

A pragmatic solution is to remove the sign and then add it again:
function toTime(seconds) {
if (seconds < 0) return "-" + toTime(-seconds);
return new Date(seconds * 1000).toISOString().substr(11, 8);
}
console.log(toTime(540));
console.log(toTime(-2820));

Just test
const convert = secs => {
const sign = secs < 0
const hhmmss = new Date(Math.abs(secs) * 1000).toISOString().substr(11, 8);
return sign ? '-' + hhmmss : hhmmss
}
console.log(convert(540));
console.log(convert(-2820));

Moment.js difference/duration from 2 times (not dates)

I don't find any docs about it on moment.js website.
I need to calculate difference from 2 duration time (not dates).
For example:
27:10 - 7:20 = 19:50
where 27 is hours (can be bigger than 24h of a day) and 10 is minutes.
I see moment.js can operatore only with dates?

You can use moment.duration()
var d1, d2, dDiff, diff;
d1 = moment.duration('7:20', 'HH:mm');
d2 = moment.duration('27:10', 'HH:mm');
dDiff = d2.subtract(d1);
diff = dDiff.get('days') + ':day(s) ' + dDiff.get('hours') + ':' + dDiff.get('minutes');
console.log(diff); // "0:day(s) 19:50"
more details: momentjs durations

function getTimeDifference(start, end) {
var s = start.split(':');
var e = end.split(':');
var d = (parseInt(s[0], 10) * 60 + parseInt(s[1], 10)) - (parseInt(e[0], 10) * 60 + parseInt(e[1], 10));
var res = parseInt((d / 60), 10).toString() + ':' + (d % 60).toString();
alert(res);
}
getTimeDifference('27:10' , '7:20');
May be helpful to you...

You can do it using pure maths
function f1(a, b) {
const [hoursA, minutesA] = a.split(':').map(v => parseInt(v, 10));
const [hoursB, minutesB] = b.split(':').map(v => parseInt(v, 10));
let minutesDiff = 60 * (hoursA - hoursB) + (minutesA - minutesB)
const hoursDiff = (minutesDiff - minutesDiff % 60) / 60;
minutesDiff = minutesDiff % 60;
return hoursDiff + ':' + minutesDiff.toString().padStart(2,'0');
}
console.log(f1('27:10','7:20'))
console.log(f1('248:10','7:05'))
or using the date object
function f2(a, b) {
const [hoursA, minutesA] = a.split(':').map(v => parseInt(v, 10));
const [hoursB, minutesB] = b.split(':').map(v => parseInt(v, 10));
const time = new Date(Date.UTC(1970));
time.setUTCHours(hoursA - hoursB, minutesA - minutesB);
return ((time - time % 86400000) / 3600000 + time.getUTCHours()) + ':' + time.getUTCMinutes().toString().padStart(2,'0');
}
console.log(f2('27:10','7:20'))
console.log(f2('248:10','7:05'))

This doesn't need a library, you just need to do some base60 arithmetic.
You simply convert both to minutes, do a subtraction and convert back to hours and minutes
//27:10 - 7:20 = 19:50
function calculateDifference(time1,time2){
var diffMins = toMinutes(time1)-toMinutes(time2);
return toHoursMinutes(diffMins);
}
function toMinutes(time){
var [hrs,mins] = time.split(':').map(x => parseInt(x,10));
return hrs*60 + mins;
}
function toHoursMinutes(mins)
{
return Math.floor(mins/60) + ":" + (mins%60).toString().padStart('0',2);
}
console.log(calculateDifference("27:10","7:20"));

Convert seconds to days, hours, minutes and seconds

I have a Javascript timing event with an infinite loop with a stop button.
It will display numbers when start button is click.Now I want this numbers converted to something like 4 hours, 3 minutes , 50 seconds
var c = 0;
var t;
var timer_is_on = 0;
function timedCount() {
document.getElementById('txt').value = c;
c = c + 1;
t = setTimeout(function() {
timedCount()
}, 1000);
}
function doTimer() {
if (!timer_is_on) {
timer_is_on = 1;
timedCount();
}
}
function stopCount() {
clearTimeout(t);
timer_is_on = 0;
}
$(".start").on("click", function() {
//var start = $.now();
//alert(start);
//console.log(start);
doTimer();
$(".end").show();
$(".hide_div").show();
});
$(".end").on("click", function() {
stopCount();
});
.hide_div {
display: none;
}
.end {
display: none;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<p class="start">Start</p>
<p class="end">End</p>
<p class="hide_div">
<input type="text" id="txt" />//display numbers eg 12345
</p>
How to convert numbers like 123456 to 1 day, 4 hours, 40 min, 45 seconds?

I suggest doing this way!:
function secondsToDhms(seconds) {
seconds = Number(seconds);
var d = Math.floor(seconds / (3600*24));
var h = Math.floor(seconds % (3600*24) / 3600);
var m = Math.floor(seconds % 3600 / 60);
var s = Math.floor(seconds % 60);
var dDisplay = d > 0 ? d + (d == 1 ? " day, " : " days, ") : "";
var hDisplay = h > 0 ? h + (h == 1 ? " hour, " : " hours, ") : "";
var mDisplay = m > 0 ? m + (m == 1 ? " minute, " : " minutes, ") : "";
var sDisplay = s > 0 ? s + (s == 1 ? " second" : " seconds") : "";
return dDisplay + hDisplay + mDisplay + sDisplay;
}

Use Math like this way, Second param in parseInt is for base, which is optional
var seconds = parseInt(123456, 10);
var days = Math.floor(seconds / (3600*24));
seconds -= days*3600*24;
var hrs = Math.floor(seconds / 3600);
seconds -= hrs*3600;
var mnts = Math.floor(seconds / 60);
seconds -= mnts*60;
console.log(days+" days, "+hrs+" Hrs, "+mnts+" Minutes, "+seconds+" Seconds");
Your given seconds 123456 would be 1 days, 10 Hrs, 17 Minutes, 36 Seconds not 1 days, 4 Hrs, 40 Minutes, 45 Seconds

function countdown(s) {
const d = Math.floor(s / (3600 * 24));
s -= d * 3600 * 24;
const h = Math.floor(s / 3600);
s -= h * 3600;
const m = Math.floor(s / 60);
s -= m * 60;
const tmp = [];
(d) && tmp.push(d + 'd');
(d || h) && tmp.push(h + 'h');
(d || h || m) && tmp.push(m + 'm');
tmp.push(s + 's');
return tmp.join(' ');
}
// countdown(3546544) -> 41d 1h 9m 4s
// countdown(436654) -> 5d 1h 17m 34s
// countdown(3601) -> 1h 0m 1s
// countdown(121) -> 2m 1s

My solution with map() and reduce():
const intervalToLevels = (interval, levels) => {
const cbFun = (d, c) => {
let bb = d[1] % c[0],
aa = (d[1] - bb) / c[0];
aa = aa > 0 ? aa + c[1] : '';
return [d[0] + aa, bb];
};
let rslt = levels.scale.map((d, i, a) => a.slice(i).reduce((d, c) => d * c))
.map((d, i) => ([d, levels.units[i]]))
.reduce(cbFun, ['', interval]);
return rslt[0];
};
const TimeLevels = {
scale: [24, 60, 60, 1],
units: ['d ', 'h ', 'm ', 's ']
};
const secondsToString = interval => intervalToLevels(interval, TimeLevels);
If you call secondsToString(123456), you can get "1d 10h 17m 36s "

Here is my solution, a simple function that will round to the nearest second!
var returnElapsedTime = function(epoch) {
//We are assuming that the epoch is in seconds
var hours = epoch / 3600,
minutes = (hours % 1) * 60,
seconds = (minutes % 1) * 60;
return Math.floor(hours) + " hours, " + Math.floor(minutes) + " minutes, " + Math.round(seconds) + " seconds";
}

Came up with my own variation to some of the solutions suggested in this thread.
if (!Number.prototype.secondsToDHM) {
Number.prototype.secondsToDHM = function() {
const secsPerDay = 86400;
const secsPerHour = 3600;
const secsPerMinute = 60;
var seconds = Math.abs(this);
var minus = (this < 0) ? '-' : '';
var days = Math.floor(seconds / secsPerDay);
seconds = (seconds % secsPerDay);
var hours = Math.floor(seconds / secsPerHour);
seconds = (seconds % secsPerHour);
var minutes = Math.floor(seconds / secsPerMinute);
seconds = (seconds % secsPerMinute);
var sDays = new String(days).padStart(1, '0');
var sHours = new String(hours).padStart(2, '0');
var sMinutes = new String(minutes).padStart(2, '0');
return `${minus}${sDays}D ${sHours}:${sMinutes}`;
}
}
var a = new Number(50000).secondsToDHM();
var b = new Number(100000).secondsToDHM();
var c = new Number(200000).secondsToDHM();
var d = new Number(400000).secondsToDHM();
console.log(a);
console.log(b);
console.log(c);
console.log(d);

This answer builds upon on Andris' approach to this question, but it doesn't have trailing commas if lesser units are not present.
It also borrows from this answer dealing with joining array values only if truthy:
https://stackoverflow.com/a/19903063
I'm not a javascript god and it's probably horribly over-engineered, but hopefully readable and correct!
function sformat(s) {
// create array of day, hour, minute and second values
var fm = [
Math.floor(s / (3600 * 24)),
Math.floor(s % (3600 * 24) / 3600),
Math.floor(s % 3600 / 60),
Math.floor(s % 60)
];
// map over array
return $.map(fm, function(v, i) {
// if a truthy value
if (Boolean(v)) {
// add the relevant value suffix
if (i === 0) {
v = plural(v, "day");
} else if (i === 1) {
v = plural(v, "hour");
} else if (i === 2) {
v = plural(v, "minute");
} else if (i === 3) {
v = plural(v, "second");
}
return v;
}
}).join(', ');
}
function plural(value, unit) {
if (value === 1) {
return value + " " + unit;
} else if (value > 1) {
return value + " " + unit + "s";
}
}
console.log(sformat(60)); // 1 minute
console.log(sformat(3600)); // 1 hour
console.log(sformat(86400)); // 1 day
console.log(sformat(8991)); // 2 hours, 29 minutes, 51 seconds
If you needed to convey the duration more 'casually' in words, you could also do something like:
var remaining_duration = sformat(117);
// if a value is returned, add some prefix and suffix
if (remaining_duration !== "") {
remaining_duration = "about " + remaining_duration + " left";
}
$(".remaining_duration").text(remaining_duration);
// returns 'about 1 minute, 57 seconds left'

I further tweaked the code by Svetoslav as follows:
function convertSecondsToReadableString(seconds) {
seconds = seconds || 0;
seconds = Number(seconds);
seconds = Math.abs(seconds);
const d = Math.floor(seconds / (3600 * 24));
const h = Math.floor(seconds % (3600 * 24) / 3600);
const m = Math.floor(seconds % 3600 / 60);
const s = Math.floor(seconds % 60);
const parts = [];
if (d > 0) {
parts.push(d + ' day' + (d > 1 ? 's' : ''));
}
if (h > 0) {
parts.push(h + ' hour' + (h > 1 ? 's' : ''));
}
if (m > 0) {
parts.push(m + ' minute' + (m > 1 ? 's' : ''));
}
if (s > 0) {
parts.push(s + ' second' + (s > 1 ? 's' : ''));
}
return parts.join(', ');
}

Short answer:
var s = (Math.floor(123456/86400) + ":" + (new Date(123456 * 1000)).toISOString().substr(11, 8)).split(":");
console.log(`${s[0]} days, ${s[1]} hours, ${s[2]} minutes, ${s[3]} seconds` )
Edit:
Let me break it down in parts :
Math.floor(123456/86400)
86400 is the the total seconds in a day (60 seconds * 60 minutes * 24 hours). Dividing the inputted seconds by this value gives us number of days. We just need the whole part so we use Math.floor because the fractional piece is handled by this part:
(new Date(123456 * 1000)).toISOString().substr(11, 8)
the explanation can be found here:
Convert seconds to HH-MM-SS with JavaScript?
It just outputs hh:mm:ss, no days. So the first part and this part is a perfect combination
We concatenate using a colon (:) as a separator. The string looks like this:
'1:10:17:36'
We split it into an array with .split(":");. Then finally, we format the elements of the array for the desired output.

I've tweaked the code that Andris posted https://stackoverflow.com/users/3564943/andris
// https://stackoverflow.com/questions/36098913/convert-seconds-to-days-hours-minutes-and-seconds
function app_ste_36098913_countdown_seconds_to_hr(seconds) {
seconds = seconds || 0;
seconds = Number(seconds);
seconds = Math.abs(seconds);
var d = Math.floor(seconds / (3600*24));
var h = Math.floor(seconds % (3600*24) / 3600);
var m = Math.floor(seconds % 3600 / 60);
var s = Math.floor(seconds % 60);
var parts = new Array();
if (d > 0) {
var dDisplay = d > 0 ? d + ' ' + (d == 1 ? "day" : "days") : "";
parts.push(dDisplay);
}
if (h > 0) {
var hDisplay = h > 0 ? h + ' ' + (h == 1 ? "hour" : "hours") : "";
parts.push(hDisplay)
}
if (m > 0) {
var mDisplay = m > 0 ? m + ' ' + (m == 1 ? "minute" : "minutes") : "";
parts.push(mDisplay)
}
if (s > 0) {
var sDisplay = s > 0 ? s + ' ' + (s == 1 ? "second" : "seconds") : "";
parts.push(sDisplay)
}
return parts.join(', ', parts);
}

You will probably find using epoch timestamps more straightforward: As detailed in Convert a Unix timestamp to time in JavaScript, the basic method is like so:
<script>
// Create a new JavaScript Date object based on the timestamp
// multiplied by 1000 so that the argument is in milliseconds, not seconds.
var date1 = new Date();
alert ('easy trick to waste a few seconds...' + date1);
// var date = date2 - date1;
// Hours part from the timestamp
var hours1 = date1.getHours();
// Minutes part from the timestamp
var minutes1 = "0" + date1.getMinutes();
// Seconds part from the timestamp
var seconds1 = "0" + date1.getSeconds();
var date2 = new Date();
// Hours part from the timestamp
var hours2 = date2.getHours();
// Minutes part from the timestamp
var minutes2 = "0" + date2.getMinutes();
// Seconds part from the timestamp
var seconds2 = "0" + date2.getSeconds();
// Will display time in 10:30:23 format
// var formattedTime = hours + ':' + minutes.substr(-2) + ':' + seconds.substr(-2);
var elapsedHrs = hours2 - hours1;
var elapsedMin = minutes2.substr(-2) -minutes1.substr(-2);
var elapsedSec = seconds2.substr(-2) - seconds1.substr(-2);
var elapsedTime = elapsedHrs + ' hours, ' + elapsedMin + ' minutes, ' + elapsedSec + ' seconds';
alert ('time between timestamps: ' + elapsedTime);
</script>
Be warned that this script needs some work since for now it will give negative values for things like date1 = 12:00:00 and date2 = 12:00:05, but I'll leave that to you fo now.
You should rewrite your code to take a timestamp ( var x = new Date(); ) at the start of your timer and one whenever you are done/want to check elapsed time, and subtract the two before parsing out elapsed seconds, minutes, hours etc as required.

This is my take at the question, even if it is an old topic.
You can use a loop to compute everything for you :
function time_remaining(date1, date2) {
let seconds = (date2 - date1) / 1000
let units = ["years", "days", "h", "min", "s"]
let limit_units = [365, 24, 60, 60, 1]
const reducer = (accumulator, curr) => accumulator * curr;
let time = []
for (let i = 0; i < units.length; i++) {
let divisor = limit_units.slice(i).reduce(reducer)
let value = Math.floor(seconds / divisor)
seconds = seconds - value * divisor
time.push(value)
}
return clean_time(time, units)
}
// at this point, you have your answer. However,
// we can improve the result by removing all none
// significative null units (i.e, if your countdown is
// only about hours, minutes and seconds, it is not
// going to include years and days.)
function clean_time(time, units) {
time = time.reverse()
while (time[time.length - 1] == 0) {
time.pop()
}
return [time.reverse(), units.slice(-time.length)]
}
let date1 = Date.parse("2023-07-09T17:50:33")
console.log(time_remaining(Date.now(), date1))

Averaging Times using Javascript

I am building an app using Phonegap and JQuery.
The app stores ( using window.localStorage ) a set of times (no more than 10) in the format.
HH:MM:SS.mm
There are a number of 'Zero' times in the list eg '00:00:00.00' which iphonegap, javascript
eliminate using..
function removeA(arr){
var what, a= arguments, L= a.length, ax;
while(L> 1 && arr.length){
what= a[--L];
while((ax= arr.indexOf(what))!= -1){
arr.splice(ax, 1);
}
}
return arr;
}
scores.sort();
removeA(scores,'00:00:00.00');
so that i'm left with the fastest time first, and only the times that have a value.
I need to produce from the remaining values the average of those times.
eg: 00:00:03.00
00:00:05.00
00:00:02.00
00:00:06.00
= 00:00:04.00
thanks in advance :)

var times= [ '00:00:03.00', '00:00:05.00', '00:00:02.00', '00:00:06.00'],
date = 0,
result = '';
function offsetify(t){
return t < 10 ? '0' + t : t;
}
for(var x = 0; x < times.length; x++ ) {
var tarr = times[x].split(':');
date += new Date(0, 0, 0, tarr[0], tarr[1], tarr[2].split('.')[0], tarr[2].split('.')[1]).getTime();
}
var avg = new Date(date/times.length);
result = offsetify(avg.getHours()) + ':' + offsetify(avg.getMinutes()) + ':' + offsetify(avg.getSeconds()) + '.' + offsetify(avg.getMilliseconds());
DEMO

if you are going to also have millisecond values and you want to consider them, then convert the times into millisecond. Now, add them and divide them by the number of records. Else, convert everything to seconds and find the average - you get the answer in seconds, of course.
The conversion is quite simple if take little time to think over it. Here's how to convert.
To milliseconds:
function convertToMS(timeStr) { // timeStr in format 'HH:MM:SS.mm'
var I = parseInt; // for brevity
var t = timeStr,
h = I( t.substr(0,2) ),
m = I( t.substr(3,2) ),
s = I( t.substr(6,2) ),
ms = I( t.substr(9,2) );
return h * 3600000 + m * 60000 + s * 1000 + ms;
}
To seconds:
function convertToS(timeStr) { // timeStr in format 'HH:MM:SS[.mm]' -- .mm is ignored.
var I = parseInt; // for brevity
var t = timeStr,
h = I( t.substr(0,2) ),
m = I( t.substr(3,2) ),
s = I( t.substr(6,2) );
return h * 3600 + m * 60 + s;
}
After the conversion's done, add them up and find the average.
UPDATE:
To convert back to the format 'HH:MM:SS.mm', we change back the time into 'chunks' of hours, minutes, seconds and (if applicable) milliseconds.
function chunkifyFromSec(time) { // time in s
var t = "",
h = Math.floor(time / 3600),
m = Math.floor( (t - (h * 3600)) / 60 ),
s = t - (h * 3600) - (m * 60);
return {
HH: h, MM: m, SS: s, mm: 0
};
}
function chunkifyFromMS(time) { // time in ms
var t = "",
h = Math.floor(time / 3600000),
m = Math.floor( (t - (h * 3600000)) / 60000 ),
s = Math.floor( (t - (h * 3600000) - (m * 60000)) / 1000 ),
mm = t - (h * 3600000) - (m * 600000) - (s * 1000);
return {
HH: h, MM: m, SS: s, mm: mm
};
}
Then, we return the string in the format 'HH:MM:SS.mm' using this:
function toTimeStr(chunks) {
return
(chunks.HH < 0 ? '0' : '') + chunks.HH + ":"
+= (chunks.MM < 0 ? '0' : '') + chunks.MM + ":"
+= (chunks.SS < 0 ? '0' : '') + chunks.SS + "."
+= (chunks.mm < 0 ? '0' : '') + chunks.mm
}

I don't have much experience with Javascript so I might have some syntax errors but I think you could do something like
var i = 0;
var totalTime = 0.0;
for (i=0; i < scores.length; i++) {
var hours = parseFloat(scores[i].substring(0, 2)); //get numeric value for hours
var minutes = parseFloat(scores[i].substring(3,5)); //get numeric value for minutes
var seconds = parseFloat(scores[i].substring(6)); //get numeric for the seconds
var time = ((hours * 60) + minutes) * 60 + seconds; //60 minutes in an hour, 60 seconds in a minute
totalTime += time;
}
var avgTime = totalTime/scores.length;
var avgHours = Math.floor(avgTime / 3600); //60*60
var avgHoursStr = String(avgHours);
var avgMinutes = Math.floor((avgTime % 3600) / 60); //mod to get rid of the hours
var avgMinutesStr = String(avgMinutes);
var avgSeconds = avgTime - avgHours*3600 - avgMinutes*60; //get the remainder. Can't use mod due to decimal
var avgSeconds = String(avgSeconds);
//Concat strings. Add the ":" spacers. Where necessary, add leading 0
var avgStr = (avgHoursStr.length > 1 ? "" : "0") + avgHoursStr + ":" + (avgMinutesStr.length > 1 ? "" : "0") + avgMinuteStr + ":" + avgSecondsStr;
[EDIT - Thanks to Parth Thakkar for point out my problem]

To return the answer in milliseconds or seconds:
var times = ["00:00:03.00", "00:00:05.00", "00:00:02.00", "00:00:06.00"];
function averageTimes(times,unit) {
if (!times) {
return false;
}
else {
var totalMilliseconds = 0, hours, minutes, seconds, milliseconds, parts;
for (var i = 0, len = times.length; i < len; i++) {
parts = times[i].split(':');
hours = parseInt(parts[0], 10) * 3600000;
minutes = parseInt(parts[1], 10) * 60000;
seconds = parseInt(parts[2].split('.')[0], 10) * 1000;
milliseconds = parseInt(parts[2].split('.')[1], 10);
totalMilliseconds += (hours + minutes + seconds + milliseconds);
}
if (!unit || unit.toLowerCase() == 'ms'){
return totalMilliseconds/times.length + ' milliseconds';
}
else if (unit.toLowerCase() == 's') {
return (totalMilliseconds/1000)/times.length + ' seconds';
}
}
}
// parameters:
// times: an array of times in your supplied format, 'HH:MM:SS:mm',
// unit: a string ('ms' or 's'), denoting whether to return milliseconds or seconds.
var average = averageTimes(times,'s');
console.log(average);​
JS Fiddle demo.
References:
for(){/*...*/} loop.
parseInt().
split().
toLowerCase().

How to get of two time values using jQuery/Javascript?

I have two values that are used for the amount of time it will take to complete a task. How can I add these values together to come up with a total number of hours and minutes, but still have the value account for 60 minutes equalling one hour?
The two values I'd like to get the sum of and the total value are in HH:MM (00:00) format.
Thanks!

Writing your own time and date functions can get complex. Why re-invent the wheel. Take a look at the excellent http://www.datejs.com/ date library. It handles all date and time related tasks and usage is very simple.

Here's something I had laying around. It allows for an infinite number of arguments, so you could have addTime('01:00') or addTime('01:00', '02:00', '03:00', '04:00'), etc. It's three functions long because it also verifies if the times entered are properly formatted, and if not, then it formats them. (E.g. Ensures that minutes is 2 digits long, and if hours is 1 digit long, then pad it with one zero, etc.)
You can play with it here: http://jsfiddle.net/WyxwU/
It's also here:
var totalTime = addTime('12:34', '56:12', '78:45');
document.write(totalTime);
function addTime()
{
if (arguments.length < 2)
{
if (arguments.length == 1 && isFormattedDate(arguments[0])) return arguments[0];
else return false;
}
var time1Split, time2Split, totalHours, totalMinutes;
if (isFormattedDate(arguments[0])) var totalTime = arguments[0];
else return false;
for (var i = 1; i < arguments.length; i++)
{
// Add them up
time1Split = totalTime.split(':');
time2Split = arguments[i].split(':');
totalHours = parseInt(time1Split[0]) + parseInt(time2Split[0]);
totalMinutes = parseInt(time1Split[1]) + parseInt(time2Split[1]);
// If total minutes is more than 59, then convert to hours and minutes
if (totalMinutes > 59)
{
totalHours += Math.floor(totalMinutes / 60);
totalMinutes = totalMinutes % 60;
}
totalTime = totalHours + ':' + padWithZeros(totalMinutes);
}
return totalTime;
}
function isFormattedDate(date)
{
var splitDate = date.split(':');
if (splitDate.length == 2 && (parseInt(splitDate[0]) + '').length <= 2 && (parseInt(splitDate[1]) + '').length <= 2) return true;
else return false;
}
function padWithZeros(number)
{
var lengthOfNumber = (parseInt(number) + '').length;
if (lengthOfNumber == 2) return number;
else if (lengthOfNumber == 1) return '0' + number;
else if (lengthOfNumber == 0) return '00';
else return false;
}

Here is the simple JS code for this,
var a = "2:50";
var b = "2:15";
var splitTimeStr = function(t){
var t = t.split(":");
t[0] = Number(t[0]);
t[1] = Number(t[1]);
return t;
};
var addTime = function(t1, t2){
var t1Hr = splitTimeStr(t1)[0];
var t1Min = splitTimeStr(t1)[1];
var t2Hr = splitTimeStr(t2)[0];
var t2Min = splitTimeStr(t2)[1];
var rHr = t1Hr + t2Hr;
var rMin = t1Min + t2Min;
if (rMin >= 60)
{
rMin = rMin - 60;
rHr = rHr + 1;
}
if (rMin < 10) rMin = "0" + rMin;
if (rHr < 10) rHr = "0" + rHr;
return "" + rHr + ":" + rMin;
};
document.write(addTime(a, b));
you can validate/play this with code here: http://jsfiddle.net/z24v7/

What you have to do is calculate them to a decimal by that I mean.
Strip out the hour/mins multiple that by 60 + to mins
//strip out the hours
l_hour = Number(l_time$.substr(0, l_pos));
//Strip out the mins
l_min = Number(l_time$.substr(l_pos + 1, l_time$.length));
//add the two values divided by 60 mins
l_time_decimal= Number(Math.abs(l_hour)) + Number(Math.abs(l_min)/60);
Do this for each value then deduct the two figures to give you the difference (i.e time taken). All thats left is convert it back from a decimal to a time
l_difference_in_min = l_difference * 60;
l_time_mins = l_difference_in_min%60;
l_time_hours = (l_difference_in_min - l_mins)/60;
Now just format the two to be HH:MM

I would break the problem into sub-tasks that are reusable. You have to concerns here:
Process a time string in "hh:mm" format: Converting this to minutes makes sense because it seems to be the time granularity at which you're operating.
Format a given number of minutes into a time string in "hh:mm" format.
The fact that you're adding two times together is a diversion from the actual two problems above.
Parse a time string into minutes:
function parseMinutes(s) {
var tokens = s.split(":");
return tokens[0] * 60 + parseInt(tokens[1]);
}
Format minutes into a time string:
function formatMinutes(minutes) {
function pad(n) {
return n > 9
? n
: ("0" + n);
}
var hours = Math.floor(minutes / 60),
mins = minutes % 60;
return pad(hours) + ":" + pad(mins);
}
Then your specific problem can be tackled by:
var sum = formatMinutes(parseMinutes(a) + parseMinutes(b));