We Keep Coding

get months difference between two dates javascript

I'm trying to compare two dates and get the number of months that exist between them, for which it uses the moment library and I get something like this:
var date1 = moment('2021-05-30');
var date2 = moment('2021-06-30');
var result = date2.diff(date1, 'months');
console.log(result);
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.18.1/moment.min.js"></script>
however within my business model there will not always be exact dates like these: '2021-05-30' to '2021-06-30' Also in the cases that have '2021-06-1' to '2021-06-15' which are like 15 days apart, I already want it to take 1 month even though there is precisely no 30 days difference, or if I have the dates '2021-06-1' to '2021-07-15' which are approximately 45 days, it already took me about 2 months, so how can I control that? any ideas? It does not matter if it is with moment or another library, I hope your help thank you very much

You can pass third param to diff function.
var result = date2.diff(date1, 'months', true);
This will return the result as decimal. Then you can use Math.ceil function to get the desired result.
var result = Math.ceil(date2.diff(date1, 'months', true));

Incorrect time while copy pasting a date time value using google apps script [duplicate]

I'm trying to get from a time formatted Cell (hh:mm:ss) the hour value, the values can be bigger 24:00:00 for example 20000:00:00 should give 20000:
Table:
if your read the Value of E1:
var total = sheet.getRange("E1").getValue();
Logger.log(total);
The result is:
Sat Apr 12 07:09:21 GMT+00:09 1902
Now I've tried to convert it to a Date object and get the Unix time stamp of it:
var date = new Date(total);
var milsec = date.getTime();
Logger.log(Utilities.formatString("%11.6f",milsec));
var hours = milsec / 1000 / 60 / 60;
Logger.log(hours)
1374127872020.000000
381702.1866722222
The question is how to get the correct value of 20000 ?

Expanding on what Serge did, I wrote some functions that should be a bit easier to read and take into account timezone differences between the spreadsheet and the script.
function getValueAsSeconds(range) {
var value = range.getValue();
// Get the date value in the spreadsheet's timezone.
var spreadsheetTimezone = range.getSheet().getParent().getSpreadsheetTimeZone();
var dateString = Utilities.formatDate(value, spreadsheetTimezone,
'EEE, d MMM yyyy HH:mm:ss');
var date = new Date(dateString);
// Initialize the date of the epoch.
var epoch = new Date('Dec 30, 1899 00:00:00');
// Calculate the number of milliseconds between the epoch and the value.
var diff = date.getTime() - epoch.getTime();
// Convert the milliseconds to seconds and return.
return Math.round(diff / 1000);
}
function getValueAsMinutes(range) {
return getValueAsSeconds(range) / 60;
}
function getValueAsHours(range) {
return getValueAsMinutes(range) / 60;
}
You can use these functions like so:
var range = SpreadsheetApp.getActiveSheet().getRange('A1');
Logger.log(getValueAsHours(range));
Needless to say, this is a lot of work to get the number of hours from a range. Please star Issue 402 which is a feature request to have the ability to get the literal string value from a cell.

There are two new functions getDisplayValue() and getDisplayValues() that returns the datetime or anything exactly the way it looks to you on a Spreadsheet. Check out the documentation here

The value you see (Sat Apr 12 07:09:21 GMT+00:09 1902) is the equivalent date in Javascript standard time that is 20000 hours later than ref date.
you should simply remove the spreadsheet reference value from your result to get what you want.
This code does the trick :
function getHours(){
var sh = SpreadsheetApp.getActiveSpreadsheet();
var cellValue = sh.getRange('E1').getValue();
var eqDate = new Date(cellValue);// this is the date object corresponding to your cell value in JS standard
Logger.log('Cell Date in JS format '+eqDate)
Logger.log('ref date in JS '+new Date(0,0,0,0,0,0));
var testOnZero = eqDate.getTime();Logger.log('Use this with a cell value = 0 to check the value to use in the next line of code '+testOnZero);
var hours = (eqDate.getTime()+ 2.2091616E12 )/3600000 ; // getTime retrieves the value in milliseconds, 2.2091616E12 is the difference between javascript ref and spreadsheet ref.
Logger.log('Value in hours with offset correction : '+hours); // show result in hours (obtained by dividing by 3600000)
}
note : this code gets only hours , if your going to have minutes and/or seconds then it should be developped to handle that too... let us know if you need it.
EDIT : a word of explanation...
Spreadsheets use a reference date of 12/30/1899 while Javascript is using 01/01/1970, that means there is a difference of 25568 days between both references. All this assuming we use the same time zone in both systems. When we convert a date value in a spreadsheet to a javascript date object the GAS engine automatically adds the difference to keep consistency between dates.
In this case we don't want to know the real date of something but rather an absolute hours value, ie a "duration", so we need to remove the 25568 day offset. This is done using the getTime() method that returns milliseconds counted from the JS reference date, the only thing we have to know is the value in milliseconds of the spreadsheet reference date and substract this value from the actual date object. Then a bit of maths to get hours instead of milliseconds and we're done.
I know this seems a bit complicated and I'm not sure my attempt to explain will really clarify the question but it's always worth trying isn't it ?
Anyway the result is what we needed as long as (as stated in the comments) one adjust the offset value according to the time zone settings of the spreadsheet. It would of course be possible to let the script handle that automatically but it would have make the script more complex, not sure it's really necessary.

For simple spreadsheets you may be able to change your spreadsheet timezone to GMT without daylight saving and use this short conversion function:
function durationToSeconds(value) {
var timezoneName = SpreadsheetApp.getActive().getSpreadsheetTimeZone();
if (timezoneName != "Etc/GMT") {
throw new Error("Timezone must be GMT to handle time durations, found " + timezoneName);
}
return (Number(value) + 2209161600000) / 1000;
}
Eric Koleda's answer is in many ways more general. I wrote this while trying to understand how it handles the corner cases with the spreadsheet timezone, browser timezone and the timezone changes in 1900 in Alaska and Stockholm.

Make a cell somewhere with a duration value of "00:00:00". This cell will be used as a reference. Could be a hidden cell, or a cell in a different sheet with config values. E.g. as below:
then write a function with two parameters - 1) value you want to process, and 2) reference value of "00:00:00". E.g.:
function gethours(val, ref) {
let dv = new Date(val)
let dr = new Date(ref)
return (dv.getTime() - dr.getTime())/(1000*60*60)
}
Since whatever Sheets are doing with the Duration type is exactly the same for both, we can now convert them to Dates and subtract, which gives correct value. In the code example above I used .getTime() which gives number of milliseconds since Jan 1, 1970, ... .
If we tried to compute what is exactly happening to the value, and make corrections, code gets too complicated.
One caveat: if the number of hours is very large say 200,000:00:00 there is substantial fractional value showing up since days/years are not exactly 24hrs/365days (? speculating here). Specifically, 200000:00:00 gives 200,000.16 as a result.

Moment.JS - Change a two digit value to milliseconds using moment

At the moment I have an input field that allows you to choose an hour by entering two digits. for example you could choose 12 for 12 hours.
Is there a way using moment to convert that number into milliseconds using MomentJS?
At the moment I am having to do the below maths. I can't see in the Moment docs that this is doable.
var timeHH = scope.session.timeHH * 3600;
This works out the seconds, then later I mulitply it by 1000 for the milliseconds value.

Is there a way using moment to convert that number into mini milliseconds using moment?
There may be, but there's absolutely no reason to use MomentJS for this, and doing so would be roundabout and inefficient. It's quite straightforward: hours * 3600000 is milliseconds. There are no weird special cases to handle, etc., unless you're handling converting a particular period of hours of a real time (say, the 10 hours from 8 p.m. December 31st 2005 GMT) and want to handle leap second insertions (there was one that night at midnight), but MomentJS doesn't do that anyway.

For this particular use case, the right thing to do is a manual calculation. For the sake of completeness and in the event you needed to do more complicated calculations, to do this with Moment, you would use the duration type. The duration type will allow you to convert from one unit value to another, and if you had to make several unit conversions instead of just this one it would be a good choice.
moment.duration(12, 'hours').asMilliseconds()
43200000
In addition to converting to milliseconds, you could convert to any other unit:
var dur = moment.duration(12, 'hours');
dur.asMilliseconds();
43200000
dur.asDays();
0.5
dur.asYears();
0.001368953503494254
In addition to the as functions, you can get the parts of the duration broken out:
var dur = moment.duration(12.5, 'hours');
dur.hours();
12
dur.minutes();
30
dur.seconds();
0
Or call humanize to get a human readable string that is an estimate of the duration's length:
var dur = moment.duration(42, 'hours');
dur.humanize();
"2 days"
You can also do math with durations. See the docs for more info: http://momentjs.com/docs/#/durations/

You can try the following hack(assuming hours in 24-Hours format) :
var momObj = moment('12', 'HH');
var x = momObj.diff(moment().startOf('day'));
console.log(x) //43200000

momentjs days difference between two GMT dates

I'm trying to get difference of days between two GMT dates using moment
but I couldn't find it.
I'm on IST(+05:30) and I have some GMT dates(-05:00) in db,
I tried using following command
temp2.diff(temp1, "days")
here is a screenshot of all the commands tried in console
there we can clears see that dates are different and still shows the difference is 0
here is how I'm initializing moment objects of 'America/New_York'
var temp1 = moment.tz(new Date('Mon Jan 25 2016 22:00:00 GMT-0600'), 'America/New_York');
var temp2 = moment.tz(new Date('Tue Jan 26 2016 00:00:00 GMT-0600'), 'America/New_York');
any help appreaciated, thanks.

Well, there is less than 24 hours difference between those dates, so it's correct. The documentation says:
By default, moment#diff will return number rounded down. If you want the floating point number, pass true as the third argument.
> temp2.diff(temp1, "days", true)
0.08333333333333333
If you don't care about the hours at all, set them to 0 before you do the comparison
> temp2.hours(0).diff(temp1.hours(0), "days")
1

A few things:
You say that you are retrieving these values from a database, but then you show us loading them via the Date constructor from a string value. If you are really storing a string in your database, especially in that particular format, then you have much larger problems than the one you asked about! Please show us precisely how you load the values from your database to begin with.
You shouldn't rely on the Date object for parsing, especially when you are already using moment, which has much better parsing routines of its own.
You said these values where in America/New_York, but then you show an offset of -0600. That's never used in that time zone. The offset for the value you showed would be -0500.
You also said "I have some GMT dates(-05:00)" - which doesn't make any sense. GMT is +00:00. GMT-0500 means "5 hours behind GMT". Thus, you no longer have a "GMT date".
Be aware that the JavaScript Date object can only use the time zone of where the code is running. You cannot run it in any other time zone.
While Felix is correct in how you can show decimals with the diff function, you should realize that diff is giving you the actual elapsed time between the two moments in time you asked about. However, you seem to be wanting to know the total number of calendar days separating the two days that the moments fall into within the named time zone. To do that, you'd need to ignore the time portion. Using startOf('day') is an easy way to do that. Consider:
var a = moment.parseZone("2016-01-25T23:00:00-05:00");
var b = moment.parseZone("2016-01-26T01:00:00-05:00");
b.diff(a, 'days', true) // 0.08333333333333333 (not what you want)
b.startOf('day').diff(a.startOf('day'), 'days') // 1 (that's better!)
moment(b).startOf('day').diff(moment(a).startOf('day'),'days') // 1 (best approach)
Note a few things with this code:
The code in the last line is the best approach, as it leaves the original values of a and b alone. Otherwise, they would be modified. (Moments are mutable.)
You seem to already have the correct local time and offset, and thus there's no need to use moment-timezone's tz function. You can just use parseZone. Of course if this was just a side effect of your example, then you could still use moment-timezone, but I'd strongly recommend against using the Date constructor still.

Calculate difference between 2 dates considering Daylight Saving Time

Given a start date, and a number of days, I need to display the end date = start date + number of days.
So I did something like this:
var endDate=new Date(startDate.getTime()+ONE_DAY);
Everything works fine, except that for 25 and 26 October gives one day less.
Ex.:
2014-01-01 + 2 days = 2014-01-03
2014-10-25 + 2 days = 2014-10-26 (here is the case I need to treat).
This difference appear because of the clock going back 1 hour. Practically 2014-10-27 00:00:00 becomes 2014-10-26 23:00:00.
A simple solution would be to compute this at another hour (example 3 AM). But I want to just display a note when this happens.
For example, if user inputs 2014-10-25, I show a popup saying [something].
Now here is the real problem... I can't seem to find any algorithm that says when clocks goes back in year X.
Example... in 2014 the day is 26 October. In 2016 is 30 October (https://www.gov.uk/when-do-the-clocks-change). Why? This date looks random to be, but I don't think it is. So... when does clock go back/forward?
EDIT: All answers/comments are helpful related to how to fix the problem. But... I already passed that stage. Now I only have an itch about "how on earth are the days when clock is changed computed?".

To find the difference between two dates in whole days, create Date objects, subtract one from the other, then divide by the milliseconds in one day and round. The remainder will only be out by 1 hour for daylight saving so will round to the right value.
You may also need a small function to convert strings to Dates:
// Return Date given ISO date as yyyy-mm-dd
function parseISODate(ds) {
var d = ds.split(/\D/);
return new Date(d[0], --d[1], d[2]);
}
Get the difference in days:
function dateDiff(d0, d1) {
return Math.round((d1 - d0)/8.64e7);
}
// 297
console.log(dateDiff(parseISODate('2014-01-01'), parseISODate('2014-10-25')));
If you want to add days to a date, do something like:
// Add 2 days to 2014-10-25
var d = new Date(2014, 9, 25);
d.setDate(d.getDate() + 2);
console.log(d); // 2014-10-27
The built–in Date object takes account of daylight saving (thought there are bugs in some browsers).

I prefer adding days this way:
var startDate = //someDate;
var endDate = new Date(startDate.getFullYear(),
startDate.getMonth(),
startDate.getDate()+1);
This way you don't have to worry about the days in the calendar.
This code add 1 day, if you want to add more, change the startDate.getDate()+1 for startDate.getDate()+NUMBER_OF_DAYS it works fine even if you are on the last day of month i.e. October 31th.
But maybe you can use #RobG solution which is more elegant than mine