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Using moment.utc() incorrectly converting the date into utc format of "days" format-Moment Javascript

I'm using moment library to convert date into a utc format. here is my date string:
var dateString = "2019-01-31T11:33:16.952+0000";
new Date("2019-01-31T11:33:16.952+0000") // o/p: Thu Jan 31 2019 03:33:16 GMT-0800 (Pacific Standard Time)
since this date is less than a week from today's date, I'm trying to display a text saying "n days ago" instead of actual date. But for some reason I'm getting a future date displayed as "6 days ago" when I do this:
moment.utc("2019-01-31T11:33:16.952+0000").local().fromNow() // shouldnt this display "5 days ago"??
Not sure why moment is not converting the date correctly, any ideas what could be wrong here?

I guess(Considering use of local() converts to your local timezone so time is deducted because you might be in -ve TimeZone) this answer is a solution you're expecting:
Ideally, you would want to pass a UTC timestamp from your server to
the client. That doesn't mean you have to switch your whole server
over to UTC, it just means that you would convert from the time in
your database to UTC on the server before sending it over the web.
Sure, it would be even better if you actually stored times in UTC, but
you said you aren't in a position to make that sort of change right
now. But let's just work off the assumption that you can't change
anything at all on the server.
We'll also assume that your server is fixed to the UTC-07:00 offset.
In real life, this would only be true for places like Arizona that
don't follow daylight saving time. So if you are in Los Angeles and
are in Pacific Time, then some of your data is based on UTC-07:00, but
some of it is based on UTC-08:00. That requires a lot more work if you
want to do it in JavaScript.
Let's also assume that the input is already a string in ISO8601
format. (If it's not, then let me know and I will adjust this code.)
var s = "2013-09-11 18:00:00"; // from action.timeStamp
var actionTime = moment(s + "-07:00", "YYYY-MM-DD HH:mm:ssZ");
var timeAgo = actionTime.fromNow(); The reason your other code didn't
work is because in the first line, you are affected by the time zone
of the browser. The zone setter in the second line just changes the
zone for formatting, not changing the actual moment in time.
Also, when you dump a moment to the console for debugging, make sure
you format it for output. Otherwise you are just looking at its
internal property values, which may or may not make sense directly.

Dates manipulation with moment.js

I receive the following date from the server:
"2018-11-21 07:00:00 UTC"
Then, I convert it using userTimzone variable (since I wish the editor would use the user timezone):
dateOfAction: moment(dateOfLoss, 'YYYY-MM-DD HH:mm Z').tz(userTimzone).unix(), So dateOfAction is 1542776400. That is: Wednesday, November 21, 2018 5:00:00 AM - and so far so good. That is the dateOfAction in UTC with after right offset
I'm using react-datetime as the calendar the edit the date, using UTC.
When performing the save action, without touching the date, the calendar output is still 1542783600, but I wish to be 1542783600 - i.e the same value as in the beginning, reverting the offset at the other direction.
How can I achieve that?

A few things:
Moment doesn't map the Z token to the string "UTC". Since you're parsing in local mode, you are actually getting a moment based on the local computer's time zone rather than UTC. Thus, change the first part of your code to:
moment.utc(dateOfLoss, 'YYYY-MM-DD HH:mm [UTC]')
The brackets are to treat UTC as a literal string, which isn't strictly required so you can omit it if you like and the result will be the same.
moment.utc(dateOfLoss, 'YYYY-MM-DD HH:mm')
There's no need to call .tz(userTimezone) if you're just going to call .unix() subsequently. Unix timestamps are always UTC based. Though it's not clear why you're asking for a Unix timestamp, as react-datetime doesn't need one.
The two values you gave in the last paragraph of your question are identical, so I'm not sure specifically what you were looking for. The time you gave is indeed 1542783600, not 1542776400.
The readme file of react-datetime describes all the options you can use. You can simply pass the moment object obtained above to the value prop. You might need to use the utc or displayTimeZone props if you want to change the behavior. You might also need to call .local() or .tz(userTimezone) on the moment object before passing it in, but I'm not certain if that is required or not for this particular component.

Convert ISO Date string to date in JavaScript

Need help to convert exactly from ISO Date string to Date:
I have an ISO string date: "2016-01-23T22:23:32.927".
But when I use new Date(dateString) to convert Date, the result is wrong:
var date = new Date("2016-01-23T22:23:32.927");
The result is: Sun Jan 24 2016 05:23:32 GMT+0700. It's not true. I want the date is 23 not 24.
Please help me. Thanks a lot!

You need to supply a timezone offset with your iso date. Since there isn't one, it assumes the date to be in GMT and when you log it out, it prints it in the timezone of your browser. I think that if you pass "2016-01-23T22:23:32.927+07:00" to new Date() you would get the value you are expecting.

JavaScript environments (browser, node,...) use a single timezone for formatting dates as strings. Usually this is your system's timezone. Based on the output you get, yours is GMT+0700.
So what happened:
The string you passed as ISO format to the Date constructor doesn't specify a timezone. In this case it is treated as UTC.
When you then output the date (I'll assume with console.log), it is converted to the timezone of your environment. In this case 7 hours where added.
If that doesn't suit you, you can change the way you output the date. This depends on what output you want, e.g.:
If you just want the UTC timezone again, you can use date.toISOString().
If you want to output it in another timezone, you can call date.getTimezoneOffset() and figure out the difference between both timezones. You'd then probably need to get the individual date parts and add/subtract the timezone difference accordingly. At this point you could consider using an existing library, taking into account their possible disadvantages.

If you're willing and able to add a dependency, I recommend using moment.js for this. It makes date handling in Javascript much more straightforward and a lot safer, and fixes your specific problem right out of the box.
To do this, 1st load it from a CDN, e.g. Moment.JS 2.14.1 minified. Then use it as follows:
var date = moment("2016-01-23T22:23:32.927");
console.log(date);
// output: Sat Jan 23 2016 22:23:32 GMT-0500
...i.e. your desired result :)
Here's a jsfiddle demonstrating this.

Use date.toUTCString()
it'll give you 23 instead of 24 as it Convert a date object to a string, according to universal time

How to change only timezone without modifying the time in momentz

I have date and time in 2016-06-21T10:00:00-07:00 format which represets 06/21/2016 5 PM in PST, I just want to change this to 06/21/2016 5 PM in EST and vice versa. How can I do it with momentz?
JSFiddle
debugger;
var dateTime = moment('2016-06-21T10:00:00-07:00');
var newDateTime = dateTime.clone();
newDateTime.tz('US/Eastern');
//dateTime = dateTime.utc();
console.log(dateTime.utcOffset());
console.log(newDateTime.utcOffset());
console.log(newDateTime.utcOffset() - dateTime.utcOffset());
//console.log(utc.format());
dateTime = dateTime.add(newDateTime.utcOffset(), 'minutes');
console.log(dateTime.format());
console.log(new Date(Date.parse(dateTime.format())).toJSON());
EDIT:
given input = 2016-06-21T08:00:00-07:00 (PST)
expected output = 2016-06-21T08:00:00-04:00 (EST)
So when I convert that to UTC then it should become
2016-06-22T15:00:00Z for PST
2016-06-22T12:00:00Z for EST

I think you are confused about how ISO8601 format works. This format always represents local time with a time zone offset. Thus 2016-06-21T10:00:00-07:00 represents June 21 2016 at 10 AM in a timezone that is currently UTC-7 (this could be US pacific, among many others).
It sounds like you want to take the local time, but put it in a new timezone. This opens up some interesting questions about why you are receiving the date in the format that you are. If the date is meant to be interpreted as an exact point on the global timeline, then the format you are receiving it in is good. If however, the date is meant to be interpreted as a local time (not relative to UTC), it might be worth considering the possibility that the format of the date needs to be changed at the source. For instance, if you are making an ajax request to an API, and it is returning a date in this format, but that date actually has no relationship to UTC, it would be good to try to change that API to only send the local time (without the offset). If you were able to do that, then the following code would work:
moment.tz('2016-06-21T10:00:00', 'America/New_York').format()
"2016-06-21T10:00:00-04:00"
If you are unable to do that, or if the date is meant to be interpreted as an exact point on the global timeline, but you wish to ignore that in your specific use case, that can be done. You will need to specify a parse format that ignores the timezone offset on your initial time stamp. The code would be as follows:
moment.tz('2016-06-21T10:00:00-07:00', 'YYYY-MM-DDTHH:mm:ss', 'America/New_York').format()
"2016-06-21T10:00:00-04:00"
You might benefit from the material in this blog post, as it covers how ISO8601 format works, and how all of moment's constructor functions work.

Checkout moment().utcOffset() You can pass in the offset as parameter to this function and the date would use that locale.
Assuming you know beforehand the utcOffsets required which in your case are -420 and -240 or -300(EST with DayLightSaving). Below can be done
var dateTime = moment('2016-06-21T10:00:00-07:00');
dateTime.utcOffset(-420).format();
"2016-06-21T10:00:00-07:00"
dateTime.utcOffset(-240).format()
"2016-06-21T13:00:00-04:00"
NOTE: With -04:00, it should 13:00:00 and not 07:00:00 - http://www.timeanddate.com/time/zones/est
EDIT: This answer was posted to the earlier version of question, where same time was needed in different timezones. If it is incorrect, kindly please elaborate on how it is.
Thanks!

momentjs: how to get the date in a specific timezone

In a nutshell I want moment to respect server's timezone. I've set my machine's timezone to Alaska but I'm passing a Brisbane timezone string to moment. Now I need moment.toDate to return a date instance in the same timezone as the one I pass in the moment constructor; e.g.
m = moment("2016-11-20T08:00:00+10:00")
m.format() // "2016-11-20T08:00:00+10:00"
m.toDate() // Sat Nov 19 2016 13:00:00 GMT-0900 (AKST)
I want to get a Date instance from moment that's in the input timezone; e.g. somehow get toDate to return Sun Nov 20 2016 08:00:00 GMT+1000 (AEST).
FWIW I have tried the same code with and without moment.tz.setDefault and while it correctly changes the format result, toDate always uses the machine's timezone!
Update
The reason I need this behaviour is that some JavaScript libraries and controls don't understand moment and only work with Date and the time/date gets skewed when presented back by them. One example, the one I'm currently dealing with, is jQuery UI date picker control. I want the date picker to show the current date as it's on the server (or on a specific timezone).
Thanks in advance.

The Date object represents the time in UTC internally, and can only use the time zone of the machine its running on when projected.
There's absolutely no way to produce a Date object that uses an arbitrary time zone. Any examples you may come across that try to manipulate the Date object (such by adding or subtracting time zone offsets) are fundamentally flawed.
Moment itself has great time zone support, including the moment-timezone extension for working with named time zones instead of just time zone offsets. But once you go back to a Date object - you're back at the mercy of the behavior of that object.
Sorry, but there's no way to achieve what you are asking. Perhaps you could elaborate as to why you wanted to do this, and I could recommend a workaround.
Update: With regards to your update, usually there is a mechanism for getting the value from a date picker as text, rather than as a date object. With the example of the jQuery UI date picker control, the onSelect event gives it to you as text already, or you can simply call .val() instead of .datepicker('getDate') to get the text out of the field. Once you have a textual value, you can then parse it with moment however you like.
Similarly, when setting the value, you don't necessarily need a Date object. You could just set the value of the textbox as a string, or you can pass a string to the setDate function.
In most cases, you won't have to go through a Date object. But if for some reason you do, then you'll need to artificially construct one with something crazy like:
var d = new Date(m.format('YYYY/MM/DD'));
Normally, I'd be against that - but if it's just there to get the pass a value to a UI control, then it's probably ok.

This will get you a moment in the same timezone as the moment string, but toDate is always in the local timezone.
d = "2016-11-20T08:00:00+10:00"
m = moment(d).utcOffset(d)
m.format()
m.toDate()