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Accessing the Locale Date format with in program automatically

Is there a function which will help us to write the date using the Locale settings in Javascript.For example in my machine as per the Locale settings the format is M/D/YYYY so in my program the date should be printed in this format. If i change my the Locale settings in computer format to YYYY-MM-DD then my program should automatically print in this format without hardcoding the format. This is the expected behavior of my program. As some of the suggestions given on using toLocaleDateString method, On using toLocaleDateString it always returns in M/D/YYYY format only even then the computer Date format is changed to YYYY-MM-DD. I searched in internet i don't find any proper answer please guide me to do this. Any help is appreciated.

Determining the day of the week for specified date in an arbitrary timezone with momentJS

Say I had an ISO date string with embedded timezone information, like "2016-08-22T13:30:00-07:00" (Here, the -07:00 specifies PST). I'm looking for an elegant way to determine what day of the week it will be in that timezone on that date and time. I've tried moment.parseZone(datestring).weekday() to no avail. How can I make moment think in terms of the timezone specified in the string, instead of wherever the server happens to be?

You can try moment(datestring).utcOffset(datestring).weekday(), check the docs for more explanation. Also there is a part of the documntation on weekday which describes it as locale aware I am not sure if it maintains the time zone of the date while converting or defaults to your local/server location, I usually uses moment.day(), if it suits your use case, you can use it instead of weekday().

javascript's Data.parse() in Chrome and Firefox

I have a very simple operation by converting a string in standard format 1985-10-11T12:23:00 (without timezone specified).
Data.parse() in chrome javascript parses it in Date object as is, but in Firefox a correction for time zone applies.
How I can ensure that in both browsers Date.parse produces result without timezone corrections?

I would suspect
new Date("1985-10-11T12:23:00").toUTCString()

I have figured that out. Date.Parse accepts information about time zone so to ensure cross-browser compartibility, time zone must be added to the zone-less time stamp.
But most commonly used Z+00 notation does not apply. as per Date Parse doc, one has to specify e.g. UTC timezone as +00:00 right after timestamp

What's the difference between datetime in ISO 8601 and UTC formats in javascript?

I pick some date and time in javascript and then want to store it on server (.NET). Dates are supposed to be in future from the current moment (so they won't be before 1970).
Having read topics here on SO I learnt it's better to store date as a string and people suggest using Date.prototype.toISOString() or Date.prototype.toUTCString().
I've read that toISOString() is not available in IE 7. And I'd like to know other differences, when I should choose one or another function.

They're for different purposes.
UTC is the primary time standard by which the world regulates clocks and time.
ISO is standard format time. ISO also supports ms in its format.
So if you want to send data to the server, send the ISO, because ISO is the standard format:
var date = new Date();
sendDate(date.toISOString());
You can also use toISOString in IE7 polyfill.

I hope it will helpful to you.
Summary About toISOString() :-
The toISOString() method returns a string in ISO format (ISO 8601 Extended Format), which can be described as follows: YYYY-MM-DDTHH:mm:ss.sssZ. The timezone is always UTC as denoted by the suffix "Z".
Refer Below link for more information about toISOString().
Date.prototype.toISOString()
Summary About toUTCString() :-
The toUTCString() method converts a date to a string, using the UTC time zone.
Refer Below link for more information about toUTCString()
Date.prototype.toUTCString()

Always use .toISOString()
They give almost the same information, but in different formats. Here is what I get on my machine.
new Date().toISOString()
"2019-10-11T18:56:08.984Z"
new Date().toUTCString()
"Fri, 11 Oct 2019 18:56:08 GMT"
There are 4 reasons .toISOString() is more often what you want than .toUTCString().
A. More convenient sorting
When you sort alphabetically, the "2019-10-11T18:56:08.984Z" pattern of .toISOString() gives you the correct date order.
B. Millisecond precision
.toISOString() provides millisecond values, whereas .toUTCString() does not.
C. Any user can interpret correctly
The .toUTCString() value may be more familiar to human end-users, but only if the language settings are suitable for them. In contrast, the .toISOString() is the same regardless of language settings.
D. Reproducibly regeneratable by software
You can easily convert the ISO date string to a Javascript Date object, and then back again, regenerating exactly the same string. This is regardless of who gave you the ISO date string, where the server is, and where you are.
This is not automatically true for the UTC string. For example, if a second instance of your app system is running in a different time zone, or language, it's .toUTCstring() may use different numbers or words (respectively) to represent the same instant in time. It will be difficult for it to create a UTCString that matches what was made by the first instance of the app, since in general it will not know the language or timezone in which the first UTC string was produced.
I think nobody needs .toUTCString()
I don't know why `.toUTCString()` exists. Its word-heavy format makes it useless for internal storage of dates in your program, because it varies depending on your language and timezone setting etc.
So maybe it is to produce something nice to display externally for the user to see? Well, not really. Anyone who is not in the London time zone will not find it very helpful.
I live in London. And even I, even if I was writing an app purely for use by me, solely on my system, and only in my home, would still not want to use .toUTCString(). Because it is showing UTC (also known as GMT). London is not always on GMT. In summer, we move to GMT+1, so the .toUTCString() result would mislead anyone who didn't notice the "GMT" and do the time adjustment in their head.
If I wanted a natural-language time, to make non-computer literate users comfortable, I would construct it manually from parts, using a library like moment.js. If I wanted a quick-and-dirty solution, I would use .toString() which at least will move to Summer time when appropriate.

How to find browser date time format [duplicate]

I have set a deadline in UTC, as shown below, and I'm wondering what exactly the toLocaleString() method will do to it on user's local machines. For instance, will it account for daylight savings if they are in a timezone that recognizes it? Or will I need to insert additional code that checks where the user is, and then fixes the displayed time?
http://javascript.about.com/library/bldst.htm
var deadline = new Date('5/1/2013 ' + "16:15" + ' UTC');
alert(deadline.toLocaleString());

In general, the answer is yes. JavaScript will represent the UTC value at the appropriate local time based on the time zone settings of the computer it is running on. This includes adjustment for DST. However, as others have pointed out, the details are implementation specific.
If you want a consistent output, I would use a library to format your dates instead of relying on the default implementation. The best library (IMHO) for this is moment.js. The live examples on their main page will give you an idea of what it can do.
UPDATE
If you are passing UTC values that you want converted to the correct local time, and that time falls into a period where the time zone rules are different than the current one - then the results will be invalid. This is crazy, but true - and by design in the ECMA spec. Read - JavaScript Time Zone is wrong for past Daylight Saving Time transition rules

We don't know what exactly the toLocaleString method does (§15.9.5.5):
This function returns a String value. The contents of the String are
implementation-dependent, but are intended to represent the Date in
the current time zone in a convenient, human-readable form that
corresponds to the conventions of the host environment’s current
locale.
But yes, most implementations will consider DST if it is active in the current local timezone. For your example I'm getting "Mittwoch, 1. Mai 2013 18:15:00" - CEST.
Will I need to insert additional code that checks where the user is, and then fixes the displayed time?
I think you can trust toLocaleString - the browser should respect the user's settings. If you want to do it manually, check out timezone.js.

As you use "UTC" the date itself will be UTC format, but the toLocaleString() takes client's locale into account, which means it'll return the date in string updated with all and every changes typical to client's regional and locale settings (DST, date/time format, etc).As JS documentation describes this: "The toLocaleString() method converts a Date object to a string, using locale settings.".If you want to avoid this, use the toUTCString() method instead.I'd also recommend reading the accepted solution for the question Javascript dates: what is the best way to deal with Daylight Savings Time? to avoid (at least, to try to avoid :) future issues related to JS, browsers and locales.Hope this helps!