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JS moment parse date format

I have a timestamp with this format 09:53:56,07-04-2021
How do I convert it to ISO format ?
I have tried
moment("09:53:56,07-04-2021").format("hh:mm:ss,mm-dd-yyyy")
I'm getting "Invalid date" message

There are two separate function calls, always executed consequently, in your code. The first of those...
moment("09:53:56,07-04-2021")
... is parsing, when Moment constructor tries to create an object from the string parameter it gets. The next call is formatting:
.format("hh:mm:ss,mm-dd-yyyy")
... when Moment uses the string argument to prepare and return a proper representation of its internal date object.
The key is that the first call cannot use the data of the second one. That's why it actually doesn't matter which format you pass there. By the time it's called Moment already misinterpreted the string - and created a messed up date object out of it.
What you need is supplying the correct format into Moment constructor as its second param, like described in the docs. There are two options:
moment('09:53:56,07-04-2021', 'HH:mm:ss,MM-DD-YYYY')
moment.utc('09:53:56,07-04-2021', 'HH:mm:ss,MM-DD-YYYY')
The last one should be used if the datetime provided is always in GMT.
Note that mm in format string means "minutes"; you need M or MM (uppercase) to refer to the "month number" instead. In this case, it's MM, as it's clear that two digits are used.

Database timestamps returning intriguing values

I am using javascript to read the values of a JSON object that is returned after a GET call.
The database that provides the values is making a timestamp like this:
26-04-2019 17:22:25;
into:
1556233200000....
How can I fix this? I have no access to the database.

This is no intriguing value. It is in epoch time.
You can simply convert it back to an ISO string by using declaring JavaScript's Date instance.
const dateValue = new Date(1556233200000);
console.log(dateValue);

That number (1556233200000) is the number of milliseconds since January 1, 1970 (1/1/1970).
More information about JavaScript date is available here: Date - JavaScript MDN.

new Date() returns relative time and not UTC time

When I go to my browser development tools and write new Date() in the console, it gives me the following
Mon Dec 18 2017 17:11:29 GMT+0200
I thought it suppose to return the UTC time.
The issue is that I have a server on AWS which writes UTC time to a DB. it writes it as a string and on the client side I do the following
const updatedMilliAgo = new Date() - new Date(timeStrFromDb);
For some reason the diff is two hours even due I check it right after the write in the server.
What am I doing wrong here?

When you use new Date(), you are constructing a Date object using the current value of the system clock where the code is executing. The Date object internally stores only a number of milliseconds since 1970-01-01T00:00:00Z (without consideration of leap seconds). In other words, Date objects are always representing the UTC time.
However - there are many functions and parameters on the Date object that work in local time. For example, when you call .toString() on a Date object, the computer's local time zone is applied to the internal UTC-based value, in order to generate a string that reflects local time.
In the case of console.log - a standard object like Date cannot be directly logged. Instead, most implementations will log a string value. How that value is created is entirely implementation specific, and not defined by the ECMAScript specification. Many implementations will return the same local-time based value that .toString() returns. Some (FireFox, for example) will return the same UTC based value that .toISOString() returns. It would be reasonable for an implementation to return the actual number of milliseconds stored (.valueOf()), or some other representation. If you need consistency, don't just log the Date object. Instead, log the output of one of its functions that returns a string or a number.
You also asked about subtracting two date objects. That will implicitly call .valueOf() on each object, subtracting their UTC-based internal values and giving you the number of milliseconds between them. The most likely problem you are encountering is with how you construct the second Date object. You didn't give an example of what timeStrFromDb consists of, but understand that how that string is formatted directly relates to how the Date object is constructed. If you aren't using a standardized format, or you aren't clear on whether the value is based on UTC or a specific offset from UTC, your string may be parsed differently than you expect.

Try to use
var d = new Date();
var n = d.toUTCString();
console.log(n)

I am late, but I didn't find the answer and I had to fight for hours vs the code... finally my solution was as simple as that:
TimeZone timeZone = TimeZone.getTimeZone(ZoneId.of("UTC"));
timeZone.setDefault(timeZone);
When you set the default timezone, all dates you create will be in that ZoneId that you specify.
I hope to help to someone.

Converting moment UTC to Local date time

I put a UTC .NET/JSON date from .net on client side. When I run the following command:
moment(value.Planet.when).utc()
The returned date from webservice:
"/Date(1469271646000)/"
I get a date in the _d parameter showing the current accurate UTC date with GMT+0300 on right side.
I want to convert this time to local time on the user machine and what ever I do, I always get the time 3 hours back.
I do this:
moment(value.Planet.when).local().format('YYYY-MM-DD HH:mm:ss')
and I get the same date time as the UTC. I don't understand how can I get momentjs to show the UTC time relative to the local time. I checked that the momentjs object is indeed UTC.
I thought that if I pass the moment.utc() function the UTC date that I've got from the webservice (originally from the database), I can just run the local() function and I'll get the accurate hour relative to my area, but it didn't work.

You can use moment(date).format('YYYY-MM-DDTHH:mm:ss');
Eg:- if you date "/Date(1469271646000)/"
ip-> moment(1469271646000).format('YYYY-MM-DDTHH:mm:ss');
op-> "2016-07-23T16:30:46"

Do not use the _d property. It is for internal use only. See this answer, the user guide, or Maggie's blog post on the subject.
As far as you question of how to convert to local time, you don't actually need to convert at all. You're already parsing the input value in local mode, so you can just use it directly:
var m = moment("/Date(1469271646000)/"); // gives you a moment object in local mode.
var s = m.format(); // lets you format it as a string. Pass parameters if you like.
var d = m.toDate(); // gives you a Date object if you really need one
Try to avoid using Date objects unless they're required by some other controls or libraries you're using. Most operations can be done strictly on moment objects.

Convert string to new Date object in UTC timeZONE

Can anyone let me know how to convert a string to a date Object with UTC time zone in ExtJs?
String is "2015-10-07T23:59:00". I would like to get the same in Date Object without changing the timezone.

First of all, your date string does not have a timezone.
When you make a JavaScript date object from a string, there are two possible outcomes you could expect:
You may want the date to be 23:59 Local (23:59 CEST in my case).
In this case, you want to use new Date("2015-10-07 23:59:00") with plain javascript (note the missing T), or Ext.Date.parse("2015-10-07T23:59:00","c");.
You may want the date to be 23:59 UTC (e.g. 01:59 CEST).
In this case, you want to use new Date("2015-10-07T23:59:00").
Of course, whenever you output the date, you have to get the date in the correct time zone as well. The console/toString will usually show it in local time. JavaScript does provide getUTC... methods if you require other time zones.
You see, using Time Zones with JavaScript is a painful experience. I would recommend to try moment.js if you need full time zone support.

You can use Ext.Date.parse.It gives Date Object as output.It syntax is:
Ext.Date.parse( String input, String format, [Boolean strict] )
For Example:
Ext.Date.parse("2015-10-07T23:59:00", "Y-m-dTH:i:s");

try
var millisFromEpoch = Date.parse('2015-10-07T23:59:00');
it will parse date in GMT timezone, Ext.date.parse use the current timezone instead