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Convert Text to Integer in JS

I am trying to use Tampermonkey to find a UTC time offset and return it as as a time. The website shows an offset which I pull here
waitForKeyElements (".UTCText", getTZ_Offset);
which returns a string
console.log ("Found timezone offset: ", tzOffset);
usually like this 08:00 It can be + or -
Then i want to convert that into actual time. Eg if UTC time is 00:00, I would like to print a string "The users time is 08:00" if the offset was +08:00.
I thought i could use momentjs to get UTC time moment().utcOffset(tzOffset) and pass the offset.
When i do that it just returns NaN
What am I doing wrong?

Multiply the part before the : by 60, and add it to the second part:
const tzOffset = '08:00';
const [hourOffset, minuteOffset] = tzOffset.split(':').map(Number);
const totalMinuteOffset = hourOffset * 60 + minuteOffset;
console.log(totalMinuteOffset);
If the input may be negative, then check that as well:
const tzOffset = '-08:00';
const [_, neg, hourOffset, minuteOffset] = tzOffset.match(/(-)?(\d{2}):(\d{2})/);
const totalMinuteOffset = (neg ? -1 : 1) * (hourOffset * 60 + Number(minuteOffset));
console.log(totalMinuteOffset);
A few time zones differ from UTC not only by hours, but by minutes as well (eg, UTC +5:30, UTC +9:30), so just parseInt, even if it worked, wouldn't be reliable everywhere.

calculate difference in dates, get difference in hours mins and seconds - ideally by js, otherwise moment.js

I've managed in calculating date differences by:
converting unix date received into js date,
Saving current date as js date,
passing both to moment.js together with their format to get diff
converting to milliseconds
difference in ms is converted to a moment and returns hours mins secs
I've run into an issue where specific versions of moment works this out, and others throws exception as nan internally when calc differences. Would love to do it using just plain js, hopefully circumventing this scenario.
Uploaded a fiddle, it doesnt run unless you comment out the moment part since didnt find a moment.js version on cdn.
I'm more after the logic and a bit of pseudocode/syntax rather than a working example. The JS version's issue is that when the calculated difference between both unix dates is then converted into a date *1000 for milliseconds, it becomes a 1970 date. also the getMinutes() in js get the literal minute at that timestamp, not to overall amount of minutes ,same for hours etc..
This is the moment JS example:
var now = new Date(Date.now()),
ms = moment(then, "DD/MM/YYYY HH:mm:ss").diff(moment(now, "DD/MM/YYYY HH:mm:ss")),
d = moment.duration(ms),
formattedMomentDateDifference = Math.floor(d.asHours()) + ":";
formattedMomentDateDifference += Math.floor(d.minutes()) + ":";
formattedMomentDateDifference += Math.floor(d.seconds());
$('#momentdifference').val(formattedMomentDateDifference);
and below is the js dates example:
var then = cleanedReceivedDate, //cleaned received date in unix
difference = Math.floor(then - now)*1000, /* difference in milliseconds */
msDifferenceInDate = new Date(difference),
hoursDiff = msDifferenceInDate.getHours(),
minutesDiff = "0"+msDifferenceInDate.getHours(),
secondsDiff = "0"+msDifferenceInDate.getSeconds(),
formattedTime = hoursDiff + ':' + minutesDiff.substr(-2) + ':' + secondsDiff.substr(-2);
$('#jsdifference').val(formattedMomentDateDifference);
JS fiddle

Matt has linked to a duplicate for moment.js, so this is just a POJS solution.
UNIX time values are seconds since the epoch, ECMAScript time values are milliseconds since the same epoch. All you need to do is convert both to the same unit (either seconds or milliseconds) and turn the difference into hours, minutues and seconds.
The UNIX time value for say 2016-10-02T00:00:00Z is 1475366400, so to get the hours, minutes and seconds from then to now in your host system's time zone, do some simple mathematics on the difference from then to now:
var then = 1475366400, // Unix time value for 2016-10-02T00:00:00Z
now = Date.now(), // Current time value in milliseconds
diff = now - then*1000, // Difference in milliseconds
sign = diff < 0? '-' : '';
diff *= sign == '-'? -1 : 1;
var hrs = diff/3.6e6 | 0,
mins = diff%3.6e6 / 6e4 | 0,
secs = diff%6e4 / 1e3 ;
// Helper to pad single digit numbers
function z(n){return (n<10?'0':'') + n}
console.log(sign + hrs + ':' + z(mins) + ':' + z(secs));
PS
Using Date.now in new Date(Date.now()) is entirely redundant, the result is identical to new Date().

Javascript time difference

I am trying to simply calculate the time difference of 5:30:00 - 2:30:00. Obviously this should result in 3:00:00
However when I execute following code in console
var a = new Date(0,0,0,5,30,0)
var b = new Date(0,0,0,2,30,0)
var c = new Date(a-b)
console.log(c.getHours() + ":" + c.getMinutes() + ":" + c.getSeconds())
The result is 4:00:00.
What is causing this problem? And how should I handle it?

Date constructor is not suitable to either represent or deal the time spans.
There are no built-in tools to handle time spans in JS, so you need to implement one yourself.
Thankfully the time string -> seconds conversion is trivial:
const timeToSec = time => time.split(':').reduce((acc, v) => acc * 60 + parseInt(v), 0);
Then you can deal with seconds:
const diffInSeconds = timeToSec('5:30:00') - timeToSec('2:30:00'); // 10800
The reverse transformation of seconds -> time string is also trivial (and tbh it's simple reversed of the timeToSec implementation) and I'm leaving it as a home work.

The reason why people get different results is timezone.
When you calculate c as the difference between two dates, you actually get a date relative to 01.01.1970. In this case, when you do:
console.log(c);
You get something like:
1970-01-01T03:00:00.000Z
This is in UTC Date format.
But now if you would display c in the local time zone:
console.log(c.toLocaleDateString()+ ' ' + c.toLocaleTimeString());
... then you get maybe this:
1-1-1970 04:00:00
If you then take the hours of that date with getHours(), you get them from the date/time as it is in your time zone, in your case you are on GMT+1, which means the outcome is 4.
To avoid this time zone conversion, use the UTC versions of the getXXXX functions, like getUTCHours. Note that some time zones have non-integer hour differences with UTC (with an half-hour part), so they would need to use getUTCMinutes as well.
Be aware that converting date differences to Date format will start to give wrong results when you cover larger spans, crossing 29 February, ...etc. Differences are best calculated by taking the date differences (in milliseconds) without conversion to Date. From there it is straightforward to calculate the number of seconds, minutes, ...etc.

I would like to assume that your question is not merely about the difference between two numbers, but it is a real problem.
Then, the answer is: without specifying the day(s), the difference between two hours is meaningless, you must always specify which day(s) you are talking about.
For example Europe, Berlin:
Sunday, 27 March 2016, 02:00:00 clocks were turned
forward 1 hour.
Like in your example, this would lead to pay someone 1 hour more than it had worked...
Sunday, 30 October 2016, 03:00:00 clocks are turned backward 1 hour
..calculating the same interval Sunday, 30 October 2016 would do the opposite.
Moreover, be aware that daylight saving time has become standard in the U.S., Canada, and most European countries. However, most of the world doesn't even use it.
Moreover, during the past, starting day and ending day of saving time has been changed from year to year, and the starting hour has been also changed, i.e. you cannot assume always 2.00 at night - so reconstruct an interval without knowing this information would not lead to a correct result.
A possible solution to calculate correctly a duration, is always to store next the Local Date/Time also the UTC Date/Time and do the calculation keeping both in account, so you have both the Timezone and the Daylight Saving Time Shift to get back the exact start date/time and ending date/time.
If you don't have this information already stored, then you should retrieve them, for example, from a online Time Database.

usage
node time_diff.js 5:30:00 2:30:00
will output: 03:00:00
code of time_diff.js:
#!/usr/bin/env node
if (!process.argv[2] || !process.argv[3]) {
console.log('usage: time_diff hh:mm:ss hh:mm:ss');
process.exit(1);
}
const timeToSec = (time) => time.split(':').reduce((acc, v) => acc * 60 + parseInt(v), 0);
const diffInSeconds = (time1, time2) => timeToSec(time2) - timeToSec(time1);
const hhmmss = (secs) => {
var minutes = Math.floor(secs / 60);
secs = secs % 60;
var hours = Math.floor(minutes / 60);
minutes = minutes % 60;
return pad(hours) + ":" + pad(minutes) + ":" + pad(secs);
function pad(num) {
return ("0" + num).slice(-2);
}
};
try {
console.log(hhmmss(diffInSeconds(process.argv[3], process.argv[2])));
}
catch (err) {
console.log('usage: time_diff hh:mm:ss hh:mm:ss');
process.exit(1);
}

Try this simple plugin to get time differences.
https://github.com/gayanSandamal/good-time
import the goodTimeDiff method from good-time.js to your project
import {goodTimeDiff} from './scripts/good-time.js'
declare an object to give settings like below. let settings = {}
now assign time values to the declared object variable. *time must be in standard format and must be a string! *'from' is optional the default value will be the browser current time.
let settings = {
'from': '2019-01-13T00:00:29.251Z',
'to': '2018-09-22T17:15:29.251Z'
}
now calllback the method called goodTimeDiff() and pass the settings object variable as a parameter.
goodTimeDiff(settings)
Finally assign the method to any variable you want.
let lastCommentedTime = goodTimeDiff(timeSettings)

a - b results in three hours, but in milliseconds. You just need to convert milliseconds to hours (which is not new Date(milliseconds)).
try: (a-b)/1000/60/60
Formatted:
var a = new Date(0,0,0,5,30,0)
var b = new Date(0,0,0,2,30,0)
var diff = (a.getTime()-b.getTime())
var h = Math.floor(diff/1000/60/60)
var m = ('0' + Math.floor((diff/1000/60)%60) ).substr(-2)
var s = ('0' + Math.floor((diff/1000)%60) ).substr(-2)
console.log(h + ':' + m + ':' + s)
EDIT
For those who want to treat a time span as a date... just get the UTC date, which means Coordinated Universal Time. In other words, don't use timezone aware methods:
var a = new Date(0,0,0,5,30,0)
var b = new Date(0,0,0,2,30,0)
var c = new Date(a-b)
console.log(c.getUTCHours() + ":" + c.getUTCMinutes() + ":" + c.getUTCSeconds())
Be aware though, this will fall apart on edge cases...

Javascript: how to add n minutes to unix timestamp

I have a unix timestamp: 1368435600. And a duration in minutes: 75 for example.
Using javascript I need to:
Convert the timestamp to a string format hours:mins (09:00)
Add n minutes to the timestamp: timestamp + 75mins
I tried the moment.js library:
end_time = moment(start_time).add('m', booking_service_duration);
booking_service_duration was 75 but it added an hour. I'd also rather not have to use another js library

To add 75 minutes, just multiply by 60 to get the number of seconds, and add that to the timestamp:
timestamp += 75 * 60
To convert to hours:mins you will have to do a bit more math:
var hours = Math.floor(timestamp/60/60),
mins = Math.floor((timestamp - hours * 60 * 60) / 60),
output = hours%24+":"+mins;

Unix time is the number of seconds that have elapsed since 1 January 1970 UTC.
To move that time forward you simply add the number of seconds.
So once you have the minutes, the new timestamp is oldTime + 60*minutes
For the conversion look up parsing libraries, there is code out there for this, do some research.

So you want to convert a timestamp you have, timestamp, to locale time string after adding some time interval, specifically minutes, to it.
Whether you have a kind of date-time string or a kind of epoch mili/seconds, just create a Date object:
const date = new Date(timestamp);
Keep in mind since what you need to do require to add/substract some numbers (your case: minutes) to another number, not some date object or some date-time string, and that number is the epoch mili/secods of your date. So, always you will need the number representation of your date in mili/seconds. JavaScript Date.prototype.getTime() does return epoch miliseconds of your date. Use it:
const miliseconds = date.getTime();
Add as many as miliseconds to it:
const newMiliseconds = miliseconds + (75 * 60 * 1000);
After that, as you said you need a date-time string, well a portion of it; locale time string, you will need to go all the way back; from numbers to date object and to a date-time string:
const newDate = new Date(newMiliseconds);
const newTimestamp = newDate.toString();
Or instead of getting the whole string of it, use the following specialized method to get the format/portion of the string representation of the date object that you like directly:
const newTimestamp = newDate.toLocaleTimeString(); // "12:41:43"
Finally, all you have to do is to just strip the last semicolon and seconds to get hours:minutes format:
const newHoursMins = newTimestamp.slice(0, -3);
Better make a function of it:
function timestampPlus(timestamp, milisecondsDifference, toStringFunc = Date.prototype.toString) {
const date = new Date(timestamp);
const miliseconds = date.getTime();
const newMiliseconds = miliseconds + milisecondsDifference;
const newDate = new Date(newMiliseconds);
const newTimestamp = toStringFunc.call(newDate); // a bit advanced stuff here to let you define once and use whatever kind to string method you want to use, defaults to toString()
return newTimestamp;
}
I left the final formatting out here. You can use this for substraction as well by pasing a negative second argument. Note the seconds argument is in miliseconds and unix timestamp varies and might given to you as seconds instead, in which case you will need to convert it to miliseconds or change the above funciton definition.
function timestampPlus(timestamp, milisecondsDifference, toStringFunc = Date.prototype.toString) {
const date = new Date(timestamp);
const miliseconds = date.getTime();
const newMiliseconds = miliseconds + milisecondsDifference;
const newDate = new Date(newMiliseconds);
const newTimestamp = toStringFunc.call(newDate); // a bit advanced stuff here to let you define once and use whatever kind to string method you want to use, defaults to toString()
return newTimestamp;
}
console.log("new Date(1368435600*1000).toLocaleTimeString(): ", new Date(1368435600*1000).toLocaleTimeString())
console.log("timestampPlus(1368435600*1000, 75*60*1000, Date.prototype.toLocaleString): ", timestampPlus(1368435600*1000, 75*60*1000, Date.prototype.toLocaleTimeString))
Apart from what you need, for last parameter, toStringFunc, your options vary and encompasses all related Date methods, the are on Date.prototype:
toString
toDateString
toTimeString
toLocaleString
toLocaleDateString
toLocaleTimeString
toIsoString
toUTCString
toGMTString
toJSON

Countdown timer with cookies

I know there have been a lot of topics like this but I just have problem to which I couldn't find the answer.
My script is:
window.onload = function(){
// 200 seconds countdown
var countdown = 14400;
//current timestamp
var now = Date.parse(new Date());
//ready should be stored in your cookie
if ( !document.cookie )
{
document.cookie = Date.parse(new Date (now + countdown * 1000)); // * 1000 to get ms
}
//every 1000 ms
setInterval(function()
{
var diff = ( document.cookie - Date.parse(new Date()) );
if ( diff > 0 )
{
var message = diff/1000 + " seconds left";
}
else
{
var message = "finished";
}
document.body.innerHTML = message;
},1000);
}
I want to make countdown timer which tells user time how much left depending on his cookie value. So far I managed to calculate difference between two values but I don't know how to make format like, let's say, "dd/mm/yy hh:mm:ss" from difference timestamp (diff). Is it possible at all?

What you want is a function that converts difference in (mili)seconds to something like
5d 4h 3m 2s
If you don't mind having a large number of days for times periods > a few months, then you could use something like this:
function human_time_difference(diff) {
var s = diff % 60; diff = Math.floor(diff / 60);
var min = diff % 60; diff = Math.floor(diff / 60);
var hr = diff % 24; diff = Math.floor(diff / 24);
var days = diff;
return days + 'd ' + hr + 'h ' + min + 'm ' + s + 's';
}
If you have the difference in miliseconds, you'll need to pass the that number divided by 1000. You can also use Math.round to get rid of fractions, but you could just as well leave them on if you want that information displayed.
Getting months and years is a little trickier for a couple of reasons:
The number of days in a month varies.
When you're going from the middle of one month to the middle of the next, the time span doesn't cover any whole months, even if the number of days > 31 (e.g. How many months are there between the 2nd of June and the 30th of July??).
If you really want the number of months between two times, the number of seconds between them is not enough. You have to use calendar logic, which requires passing in the start and end date + time.
PS: When you post a question, avoid irrelevant details. For example, your question has nothing to do with cookies, setInterval, or onload handlers. The only part that you don't know is how to convert (mili)seconds to days, hours, etc. It might be helpful to supply some background on why you're trying to do something, but if it's not essential to understand the basic question, put it at the end so that people don't have to wade through it before getting to the essential part. The same advice applies to your title; make sure it's relevant by excluding irrelevant details (e.g. cookies and counting down).

JavaScript doesn't have any built in date formatting methods like you might expect if you've done any PHP. Instead, you have to build the string manually. However, there are a number of getter methods that will be useful to this end. See 10 ways to format time and date using JavaScript.
Also, just so you know. Date.parse doesn't return the millisecond portion of the time stamp (it rounds down). If you need the milliseconds, you can do either of the following
var d = new Date();
var timestamp_ms = Date.parse(d) + d.getMilliseconds();
or just
var timestamp_ms = +d;

I do not understand why you check the cookie by if ( !document.cookie ) But it doesnot work on my browser so I modified it into if ( document.cookie )
Try toString function and other. Look them up in javascript Date object reference. For example,
var t = new Date;
t.setTime(diff);
var message = t.toTimeString() + " seconds left";
This will print 11:59:58 seconds left on my browser.