Add two string time values (HH:mm:ss) with javascript

add_two_times.js

/**
 * Add two string time values (HH:mm:ss) with javascript
 *
 * Usage:
 *  > addTimes('04:20:10', '21:15:10');
 *  > "25:35:20"
 *  > addTimes('04:35:10', '21:35:10');
 *  > "26:10:20"
 *  > addTimes('30:59', '17:10');
 *  > "48:09:00"
 *  > addTimes('19:30:00', '00:30:00');
 *  > "20:00:00"
 *
 * @param {String} startTime  String time format
 * @param {String} endTime  String time format
 * @returns {String}
 */
function addTimes (startTime, endTime) {
  var times = [ 0, 0, 0 ]
  var max = times.length

  var a = (startTime || '').split(':')
  var b = (endTime || '').split(':')

  // normalize time values
  for (var i = 0; i < max; i++) {
    a[i] = isNaN(parseInt(a[i])) ? 0 : parseInt(a[i])
    b[i] = isNaN(parseInt(b[i])) ? 0 : parseInt(b[i])
  }

  // store time values
  for (var i = 0; i < max; i++) {
    times[i] = a[i] + b[i]
  }

  var hours = times[0]
  var minutes = times[1]
  var seconds = times[2]

  if (seconds >= 60) {
    var m = (seconds / 60) << 0
    minutes += m
    seconds -= 60 * m
  }

  if (minutes >= 60) {
    var h = (minutes / 60) << 0
    hours += h
    minutes -= 60 * h
  }

  return ('0' + hours).slice(-2) + ':' + ('0' + minutes).slice(-2) + ':' + ('0' + seconds).slice(-2)
}

There is a bug, if you try something like
addTimes('04:35:10', '21:35:10');
you've got 25:70:20

I fix it like it (from 30 line)

res = (minutes / 60) | 0;
hours += res;
minutes = minutes - (60 * res);

And if you need zero when minutes less then 10, like in my case
('0' + minutes).slice(-2);

@grey-mise nice!

hey hi dude i used this for my requirement to add 2 time fields contains only hours and minutes i got issue
below is fix for it

let take like addTimes('04:50', '21:20');

for (var i = 0; i < 2; i++) {
times1[i] = (isNaN(parseInt(times1[i]))) ? 0 : parseInt(times1[i])
times2[i] = (isNaN(parseInt(times2[i]))) ? 0 : parseInt(times2[i])
times[i] = times1[i] + times2[i];
}

        //var seconds = times[2];
        var minutes = times[1];
        var hours = times[0];

        //if (seconds % 60 === 0) {
        //    hours += seconds / 60;
        //}

        if (minutes >= 60) {
            //res = minutes / 60;
            //hours += res;
            //minutes = minutes - (60 * res);
            res = (minutes / 60) | 0;
            hours += res;
            minutes = minutes - (60 * res);

            minutes = minutes < 10 ? "0" + minutes : minutes;

        }


        result = hours + ':' + minutes;

I have updated the gist, now it's more concise and covers more use cases.

Examples:

addTimes('04:20:10', '21:15:10')
// "25:35:20"
addTimes('04:35:10', '21:35:10')
// "26:10:20"
addTimes('30:59', '17:10')
// "48:09:00"
addTimes('00:19:11', '13')
// "13:19:11"

Thanks for your feedback!

There is bug in your code try below

addTimes('19:30:00', '00:30:00')
// "19:60:00"

To correct this add greater than equal to both:
if (seconds >= 60) { var m = (seconds / 60) << 0 minutes += m seconds -= 60 * m }
if (minutes >= 60) { var h = (minutes / 60) << 0 hours += h minutes -= 60 * h }
Result:
addTimes('19:30:00', '00:30:00')
// "20:00:00"

@AjeshM thanks!

Hi, for my use case I needed to add support for 24hour calculation so for instance 11:55 + 14:00 = 01:55. Therfore I added the foolowing statement:

if(hours >= 24){
hours = hours %24;
hours = hours < 0 ? 24 + hours : +hours;
}

I have published https://github.com/joseluisq/timelite
Feedback welcome!

There is a problem when sum more than 99 hours. You can fix just change to -3 (or how many fields you will use, example: if 1000+ hours, you should use -4) in this line: return ('0' + hours).slice(-2) + ':' + ('0' + minutes).slice(-2) + ':' + ('0' + seconds).slice(-2)

I think for this return ('0' + hours).slice(-2) + ':' + ('0' + minutes).slice(-2) + ':' + ('0' + seconds).slice(-2) you should write this :
hours = (hours < 10) ? 0${hours} : hours
minutes = (minutes < 10) ? 0${minutes} : minutes
seconds = (seconds < 10) ? 0${seconds} : seconds
return ${hours}:${minutes}:${seconds}

because for sum more than 99 hours, result is incorrect

You are missing radis parameter in parse int

If radix is undefined or 0 (or absent), JavaScript assumes the following: If the input string begins with "0x" or "0X", radix is 16 (hexadecimal) and the remainder of the string is parsed. If the input string begins with "0", radix is eight (octal) or 10 (decimal).

Just implement your code in this tools https://vanpariyar.github.io/useful-tools

Thank you so much ...

Thank you!

If there is a need for longer hours, not only 2 digits like in my case, you can change in the return of the hours from split(-2) to split(-3)

return ('0' + hours).slice(-3) + ':' + ('0' + minutes).slice(-2) + ':' + ('0' + seconds).slice(-2)

Actually some company out there thinks the opposite
( regarding what is the meaning of shorter form ).

from opensource projects I can name ffmpeg, for example.

that shorter form means there are only the smaller units not the bigger ones :-D

So to turn that mode on here:
//4 lines:
//beggining:

function addTimes (startTime, endTime, shortMeansSmaller) {
	var s = shortMeansSmaller;

// and then line 8 as is (i cite here it as first line)

//8th line:
  var b = (endTime || '').split(':')
  if(s) { if(a.length <3){var l = a.length; var t=[]; for(var i=0; i<l; i++) t.push(a.pop()); for(var i=0; i<3-l; i++) a.push(0); for(var i=0; i<l; i++) a.push(t.pop());}
  if(b.length <3){var l = b.length; var t=[]; for(var i=0; i<l; i++) t.push(b.pop()); for(var i=0; i<3-l; i++) b.push(0); for(var i=0; i<l; i++) b.push(t.pop()); }
  }

Then with the data:

var tm = ['13:22', '56:19', '1:22:13', '47:19', '24:49', '26:55', '1:09:02', '43:38', '17:53', '1:08:45', '52:44', '32:41', '55:25'];

This

var tn = []; for(var t =0; t<tm.length-1; t+=2){ tn.push(addTimes(tm[t], tn[t+1]));
if(tm.length/2>tn.length) tn.push(tm[tm.length-1]);
//tn:
//['69:41:00', '48:41:13', '51:44:00', '44:47:02', '19:01:45', '85:25:00', '55:25']

Turns into this:

var tn = []; for(var t =0; t<tm.length-1; t+=2) tn.push(addTimes(tm[t], tm[t+1], 1));
if(tm.length/2>tn.length) tn.push(tm[tm.length-1]);
//tn
// ['01:09:41', '02:09:32', '00:51:44', '01:52:40', '01:26:38', '01:25:25', '55:25']

I think there is another bug 🐞:

When the hour part of the sum is more than two digits, then only the last two digits of the hour value is returned-

For example,

addTimes("99:00:00","01:0:0") // returns '00:00:00' instead of '100:00:00'

This can be fixed by not using slice(-2) on hour value in the return expression return ('0' + hours).slice(-2) + ':' + ('0' + minutes).slice(-2) + ':' + ('0' + seconds).slice(-2)

I fixed this by replacing the return expression to this-

 return Number('0' + hours) + ':' + ('0' + minutes).slice(-2) + ':' + ('0' + seconds).slice(-2)

✅ Here is the complete code with this minor tweak:

/**
 * Add two string time values (HH:mm:ss) with javascript
 *
 * Usage:
 *  > addTimes('04:20:10', '21:15:10');
 *  > "25:35:20"
 *  > addTimes('04:35:10', '21:35:10');
 *  > "26:10:20"
 *  > addTimes('30:59', '17:10');
 *  > "48:09:00"
 *  > addTimes('19:30:00', '00:30:00');
 *  > "20:00:00"
 *
 * @param {String} startTime  String time format
 * @param {String} endTime  String time format
 * @returns {String}
 */
function addTimes(startTime, endTime) {
  var times = [0, 0, 0];
  var max = times.length;

  var a = (startTime || '').split(':');
  var b = (endTime || '').split(':');

  // normalize time values
  for (var i = 0; i < max; i++) {
    a[i] = isNaN(parseInt(a[i])) ? 0 : parseInt(a[i]);
    b[i] = isNaN(parseInt(b[i])) ? 0 : parseInt(b[i]);
  }

  // store time values
  for (var i = 0; i < max; i++) {
    times[i] = a[i] + b[i];
  }

  var hours = times[0];
  var minutes = times[1];
  var seconds = times[2];

  if (seconds >= 60) {
    var m = (seconds / 60) << 0;
    minutes += m;
    seconds -= 60 * m;
  }

  if (minutes >= 60) {
    var h = (minutes / 60) << 0;
    hours += h;
    minutes -= 60 * h;
  }

  return (
    Number('0' + hours) +
    ':' +
    ('0' + minutes).slice(-2) +
    ':' +
    ('0' + seconds).slice(-2)
  );
}

After the update:

addTimes("99:00:00","01:0:0") // returns  the correct output '100:00:00'

I really liked your solution, and I appreciate it so much, it saved me lots of time.
If you may allow me to inform you a bug I found.

My scenario was that I have two inputs one for the checkIn time and another one for checkOut time,
users select the checkIn time so that the checkOut time - which will be 45mins after the checkIn time- can be displayed at the other input checkout input.
I found a bug when the users chose a AM time value, as your function returns an invalid value which won't be displayed at the checkout

After investigation I found that:
when I pass the startTime which is 07:00 for example and the endTime 00:45 your function returns 7:45 which is invalid for inputs 07:45 is the valid one

so I've modified the returned value in my code to look something like this
const formattedHours = Number("0" + hours).toString().length === 2 ? Number("0" + hours) :0${Number("0" + hours)}return formattedHours + ":" + ("0" + minutes).slice(-2);

And it solved my problem, and the checkout value displayed properly at the checkOut input.