Develop Reference

How can I create a Date from string, ignoring any timezone offsets?

The server uses +03:00 timezone. It offers me a date in this format: "2017-04-12T00:00:00+03:00"
I then create a new Date from this string:
options.startDate = new Date("2017-04-12T00:00:00+03:00")
But because on the client there is a different timezone, the result is actually:
Tue Apr 11 2017 23:00:00 GMT+0200 (Central Europe Daylight Time)
This brings me back one day and it's a big deal for me. Is there an elegant way to avoid this and create the same Date and Time in javascript, ignoring the timezone offset?

The date you have in options.startDate is the correct one. What you want is to display it as if you were from the same timezone as the server.
If you now server's timezone in the client script then I would considere using a library like moment.js. It would allow you to format date in the timezone you want (GMT for instance, or the one of the server).
Using both moment.js and its plugin timezone code could be :
moment("2017-04-12T00:00:00+03:00").tz("America/Los_Angeles").format();

You should never use the Date constructor or Date.parse to parse strings due to browsers differences. Even if you remove the timezone from the string and parse the remainder, e.g.
console.log( new Date('2017-04-12T00:00:00+03:00'.substr(0,19)).toString() );
you'll get different results in different browsers (e.g. Firefox and Safari).
If you don't want to use a library, use a simple function (see below). However, if you remove the timezone, the string will represent a different moment in time in each timezone with a different offset.
function parseISOIgnoreTimezone(s) {
var b = s.split(/\D/);
return new Date(b[0], b[1]-1, b[2], b[3], b[4], b[5]);
}
console.log(parseISOIgnoreTimezone('2017-04-12T00:00:00+03:00').toString());

I really recommend #VictorDrouin his answer.
But if for some reason you don't want moment.js or fiddle around with it you can use this 'hack'
new Date("2017-04-12T00:00:00+03:00".match(/\d{4}\-\d{2}\-\d{2}T\d{2}:\d{2}:\d{2}/).pop());
What it does it matches the date against given regex date format, and then supplies it to the date parser which makes it a date.
Be careful when supplying it back to the database that you supply it back without timezone offset.
var stringdate = "2017-04-12T00:00:00+03:00";
function getDate(str_date) {
var matched = str_date.match(/\d{4}\-\d{2}\-\d{2}T\d{2}:\d{2}:\d{2}/).pop();
return new Date(matched);
}
console.log(getDate(stringdate));

momentJs parse Date: Unexpected behaviour

Using momentJs I've come across something I don't understand;
let's play around with one particular date, for example 2099-11-11T15:00
Convert Moment to Date:
> moment('2099-11-11T15:00').toDate()
// => Wed Nov 11 2099 15:00:00 GMT+0100 (CET)
Convert Date to Moment:
> var d = new Date('2099-11-11T15:00')
// => undefined
> moment(d)
// => { ... _d: Wed Nov 11 2099 16:00:00 GMT+0100 (CET) }
We have different dates, the first one is wednesday at 15:00 but the second one is wednesday at 16:00. Indeed if we compare them:
moment(d).isSame(moment('2099-11-11T15:00'))
// => false
At first look I thought it was something related with toDate() method but it's not; let's type the following:
new Date('2099-11-11T15:00').toISOString()
'2099-11-11T15:00:00.000Z'
moment('2099-11-11T15:00').toISOString()
'2099-11-11T14:00:00.000Z'
What's going on here?

A few things:
Do not pay attention to the _d field. Underscored fields are internal to moment's API, and may not always be what you expect. In many functions, it has to be evaluated in combination with other internal fields (such as _offset) in order to produce a valid output. Instead, use the various public functions, such as format, toDate, .valueOf, and others.
Recognize there are many difference between how the Date constructor parses strings and how moment's parsing functions work. Don't expect them to match.
When a string doesn't contain any time zone information, moment(...) will always treat it as local, while moment.utc(...) will treat it as UTC. (Your answer gives a good example of that.)
When the Date constructor is given a string, the format of the string can affect the interpretation significantly. The actual behavior can vary across implementations, but most current browsers will see the hyphens and the T as an indication that the string is in ISO8601 format. However without any trailing Z or offset, the ES5 spec says to interpret those as UTC. This has changed for ES6, which will treat those cases as local time - to better conform with the ISO8601 spec. Since it's not clear when various environments will start to implement this change, it's prudent to not rely on the Date constructor.
If you wanted the Date constructor to interpret your value as local time (with ES5), one approach is to use string replacements to remove the T and swap the hyphens (-) with slashes (/). This works in the majority of environments, though there is no specification around this. (I've been told it fails in some Safari browsers.) Really, I would just use Moment's parsing functions, and not rely on the Date constructor at all.

Finally I decided to use moment.utc(...) instead of moment() for every operation, doing so, both times are the same:
var d = new Date('2099-11-11T15:00')
var m = moment.utc('2099-11-11T15:00')
m.isSame(moment.utc(d))
// => true

is there any workaround for broken v8 date parser?

V8 Date parser is broken:
> new Date('asd qw 101')
Sat Jan 01 101 00:00:00 GMT+0100 (CET)
I can use fragile regular expression like this:
\d{1,2} (jan|feb|mar|may|jun|jul|aug|sep|oct|nov|dec) \d{1,4}
but it is too fragile. I cannot rely on new Date (issue in V8) and also moment cant help me because moment is getting rid off date detection (github issue-thread).
is there any workaround for broken v8 date parser?
To be clear. We have Gecko and V8, both have Date. V8 has broken Date, Gecko has working one. I need the Date from in Gecko (Firefox).
Update: It’s definitely broken parser https://code.google.com/p/v8/issues/detail?id=2602
nope, Status: WorkingAsIntended

Date objects are based on a time value that is the number of milliseconds since 1 January, 1970 UTC and have the following constructors
new Date();
new Date(value);
new Date(dateString);
new Date(year, month[, day[, hour[, minutes[, seconds[, milliseconds]]]]]);
From the docs,
dateString in new Date(dateString) is a string value representing a date. The string should be in a
format recognized by the Date.parse() method (IETF-compliant RFC 2822
timestamps and also a version of ISO8601).
Now looking at the v8 sourcecode in date.js:
function DateConstructor(year, month, date, hours, minutes, seconds, ms) {
if (!%_IsConstructCall()) {
// ECMA 262 - 15.9.2
return (new $Date()).toString();
}
// ECMA 262 - 15.9.3
var argc = %_ArgumentsLength();
var value;
if (argc == 0) {
value = %DateCurrentTime();
SET_UTC_DATE_VALUE(this, value);
} else if (argc == 1) {
if (IS_NUMBER(year)) {
value = year;
} else if (IS_STRING(year)) {
// Probe the Date cache. If we already have a time value for the
// given time, we re-use that instead of parsing the string again.
var cache = Date_cache;
if (cache.string === year) {
value = cache.time;
} else {
value = DateParse(year); <- DOES NOT RETURN NaN
if (!NUMBER_IS_NAN(value)) {
cache.time = value;
cache.string = year;
}
}
}
...
it looks like DateParse() does not return a NaN for for a string like 'asd qw 101' and hence the error. You can cross-check the same with Date.parse('asd qw 101') in both Chrome(v8) [which returns -58979943000000] and Gecko (Firefox) [which returns a NaN]. Sat Jan 01 101 00:00:00 comes when you seed new Date() with a timestamp of -58979943000000(in both browsers)
is there any workaround for broken v8 date parser?
I wouldnt say V8 date parser is broken. It just tries to satisfy a string against RFC 2822 standard in the best possible way but so does gecko and both break gives different results in certain cases.
Try new Date('Sun Ma 10 2015') in both Chrome(V8) and Firefox(Gecko) for another such anomaly.
Here chrome cannot decide weather 'Ma' stands for 'March' or 'May' and gives an Invalid Date while Firefox doesnt.
Workaround:
You can create your own wrapper around Date() to filter those strings that V8's own parser cannot. However, subclassing built-ins in ECMA-5 is not feasible. In ECMA-6, it will be possible to subclass built-in constructors (Array, Date, and Error) - reference
However you can use a more robust regular expression to validate strings against RFC 2822/ISO 8601
^(?:(?:31(\/|-|\. |\s)(?:0?[13578]|1[02]|(?:Jan|Mar|May|Jul|Aug|Oct|Dec)))\1|(?:(?:29|30)(\/|-|\.|\s)(?:0?[1,3-9]|1[0-2]|(?:Jan|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec))\2))(?:(?:1[6-9]|[2-9]\d)?\d{2})$|^(?:29(\/|-|\.|\s)(?:0?2|(?:Feb))\3(?:(?:(?:1[6-9]|[2-9]\d)?(?:0[48]|[2468][048]|[13579][26])|(?:(?:16|[2468][048]|[3579][26])00))))$|^(?:0?[1-9]|1\d|2[0-8])(\/|-|\.|\s)(?:(?:0?[1-9]|(?:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep))|(?:1[0-2]|(?:Oct|Nov|Dec)))\4(?:(?:1[6-9]|[2-9]\d)?\d{2})$
Image generated from debuggex
So, seems like v8 aint broken, it just works differently.
Hope it helps!

You seem to be asking for a way to parse a string that might be in any particular format and determine what data is represented. There are many reasons why this is a bad idea in general.
You say moment.js is "getting rid of date detection", but actually it never had this feature in the first place. People just made the assumption that it could do that, and in some cases it worked, and in many cases it didn't.
Here's an example that illustrates the problem.
var s = "01.02.03";
Is that a date? Maybe. Maybe not. It could be a section heading in a document. Even if we said it was a date, what date is it? It could be interpreted as any of the following:
January 2nd, 2003
January 2nd, 0003
February 1st, 2003
February 1st, 0003
February 3rd, 2001
February 3rd, 0001
The only way to disambiguate would be with knowledge of the current culture date settings. Javascript's Date object does just that - which means you will get a different value depending on the settings of the machine where the code is running. However, moment.js is about stability across all environments. Cultural settings are explicit, via moment's own locale functionality. Relying on the browser's culture settings leads to errors in interpretation.
The best thing to do is to be explicit about the format you are working with. Don't allow random garbage input. Expect your input in a particular format, and use a regex to validate that format ahead of time, rather then just trying to construct a Date and seeing if it's valid after the fact.
If you can't do that, you'll have to find additional context to help decide. For example, if you are scraping some random bits of the web from a back-end process and you want to extract a date from the text, you'd have to have some knowledge about the language and locale of each particular web page. You could guess, but you'd likely be wrong a fair amount of the time.
See also: Garbage in, garbage out

ES5 15.9.4.2 Date.parse: /.../ If the String does not conform to
that format the function may fall back to any implementation-specific
heuristics or implementation-specific date formats. Unrecognizable
Strings or dates containing illegal element values in the format
String shall cause Date.parse to return NaN.
So that's all right and according to the citation above result of v8 date parser:
new Date('asd qw 101') : Sat Jan 01 101 00:00:00 GMT+0100
(CET)
new Date('asd qw') : Invalid Date

JavaScript: Difference between toString() and toLocaleString() methods of Date

I am unable to understand the difference between the toString() and toLocaleString() methods of a Date object in JavaScript. One thing I know is that toString() will automatically be called whenever the Date objects needs to be converted to string.
The following code returns identical results always:
​var d = new Date();
document.write( d + "<br />" );
document.write( d.toString() + "<br />" );
document.write( d.toLocaleString() );
​
And the output is:
Tue Aug 14 2012 08:08:54 GMT+0500 (PKT)
Tue Aug 14 2012 08:08:54 GMT+0500 (PKT)
Tue Aug 14 2012 08:08:54 GMT+0500 (PKT)

https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Date/toLocaleString
Basically, it formats the Date to how it would be formatted on the computer where the function is called, e.g. Month before Day in US, Day before Month in most of the rest of the world.
EDIT:
Because some others pointed out that the above reference isn't necessary reliable, how's this from the ECMAScript spec:
15.9.5.2 Date.prototype.toString ( )
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.
15.9.5.5 Date.prototype.toLocaleString ( )
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.
Since you can hopefully assume that most implementations will reflect the specification, the difference is that toString() is just required to be readable, toLocaleString() should be readable in a format that the should match the users expectations based on their locale.

Converts a date to a string, using the operating system's locale's
conventions.
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Date/toLocaleString
toLocaleString behaves similarly to toString when converting a year
that the operating system does not properly format.

I am just checked in console of the Chrome for date and found the difference in the presentation format. Hope this could help.
var d = new Date();
console.log(d.toLocaleString()); //"04.09.2016, 15:42:44"
console.log(d.toString()); //"Sun Sep 04 2016 15:42:44 GMT+0300 (FLE Daylight Time)"

Lots of references, but none are authoritative. Note that Mozilla's documentation is for JavaScript, which is their version of ECMAScript for browsers. Other browsers use other implementations and therefore, while the MDN documentation is useful, it is not authoritative (it is also a community wiki, so not even official Mozilla documentation) and does not necessarily apply to other browsers.
The definitive reference is the ECMAScript Language specification, where the behaviour of both Date.prototype.toString and Date.prototype.toLocaleString are explained in browser independent terms.
Notable is the for both methods, the string is implementation dependent, which means that different browsers will return different strings.

Just to add. Apart from Date, it also converts/formats the normal variable.
Both functions used to format/convert the passed parameter to string but how parameter is formatted is the point to look on.
toLocalestring() used to return the formatted string based on which geography the function is called.
For the sake of simplicity.
Take this example.
It shows how toString() won't format the variable but toLocaleSting() will format it based on locale setting of the geography.
let number = 1100;
console.log(number.toString()); // "1100"
console.log(number.toLocaleString()) // 1,100
let number = 1100;
console.log(number.toString());
console.log(number.toLocaleString());
It is a great help for programmer in order to avoid to write extra function to format the string or Date. toLocaleString() will take care of this.
Hope you would find it somewhat helpful & interesting.

Invalid date/None showing up for JS Date object in IE/Firefox

I am displaying a date time object in a table however for some reason in IE it display as None or Invalid Date is there something wrong with my format or is there an easy way for making this more readable such as mm/dd/yyyy HH:MM
this is what displays in chrome:
Mon Nov 28 2011 16:00:00 GMT-0500 (EST)
This is being converted from a Unix timestamp to that output in an API layer.

Probably the creation of the Date object fails, because the new Date() constructor accepts just some limited, implementation-dependent set of date strings.
You can use the Globalize library to deal with such issues, even if no localization in the usual sense is involved—but dealing with different string presentations of dates as is localization of a kind. It first looks a bit messy (it takes some time to dig into it—my book “Going Global with JavaScript and Globalize.js” contains a more readable description of it, with many examples), and it’s far from perfect, but it’s very useful.
If you know that your timestamp data is of some known exact format, you can parse it easily and then output it according to your own format descriptor. Assuming, for the sake of definiteness, that the format is the one exemplified with
Mon Nov 28 2011 16:00:00 GMT-0500 (EST)
(I know it’s an output format you mentioned, but I just use it as an example), you would first do simple string operation to discard the “GMT” and “(EST)” part (Globalize cannot currently handle them), producing e.g.
Mon Nov 28 2011 16:00:00 -05:00
and then you would just use code like the following:
var foo = Globalize.parseDate(timestamp,'ddd MMM d yyyy HH:mm:ss zzz');
var out = Globalize.format(foo,'MM/dd/yyyy HH:MM');
document.write(out);

just make your own method to format the date as string so you pass all problems with diffrent browsers and plateforms

I suspect Chrome is being helpful here and calling the .toString() method for you.
The Date object has several methods for formatting string output. See the w3schools reference page for examples.