Unable to find timezone abbreviation from Date.prototype.toString() #162

Closed
ghost opened this Issue Feb 6, 2012 · 28 comments
@ghost

Hello I came across the moment.js site via a forum and clicked my way through it, when I came across the unit test - which failed 2 tests what I want to report here:

UserAgent:
Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.7 (KHTML, like Gecko) Chrome/16.0.912.77 Safari/535.7 (Chrome 16.0.912.77 m)

Timezone:
UTC+1

Failed tests (# 28):
http://pastebin.com/bQsDuxdH

*Title edited by timrwood

@timrwood
Moment.js member

Hmm, looks like the timezone abbreviation is failing. Sorry to do remote debugging, but what is the output of the following in chrome?

new Date().toString()

Also, what is the name of the timezone you are in?

@Sertion

I get the same error in the unit-tests and I'm in UTC+1 (previously known as GMT+1) as well.

new Date().toString() prints "Sat Feb 11 2012 02:15:10 GMT+0100" in Firefox 10, "Sat Feb 11 2012 02:18:29 GMT+0100 (W. Europe Standard Time)" in Chrome 16 and "Sat Feb 11 02:18:59 UTC+0100 2012" in Internet Explorer 9

@timrwood
Moment.js member

Hmm, I was afraid of this. The problem is that Date.prototype.toString returns such different results. That is the only place to get the timezone name (PST, CST, EST, etc). If this method is not returning any timezone information (as is the case with FF10 and IE9, there is no way to get it.

Perhaps it's time to depreciate? Or is it acceptable to just note the issue in the docs?

This was referenced Feb 20, 2012
@bravedick

4318 passed, 2 failed. 2715 milliseconds.

Mozilla/5.0 (Windows NT 6.1) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.56 Safari/535.11

UTC +2 (Kyiv, Ukraine)

format timezone 2 passed,2 failed.
---> Something like "PST"
AssertionError: ---> Something like "PST"
at Object.ok (http://momentjs.com/js/tests.js?_=120203_183019:1526:39)
at http://momentjs.com/js/tests.js?_=120203_183019:2413:14
at Object.runTest (http://momentjs.com/js/tests.js?_=120203_183019:1702:9)
at http://momentjs.com/js/tests.js?_=120203_183019:1748:25
at http://momentjs.com/js/tests.js?_=120203_183019:1006:13
at http://momentjs.com/js/tests.js?_=120203_183019:616:13
at http://momentjs.com/js/tests.js?_=120203_183019:627:25
at http://momentjs.com/js/tests.js?_=120203_183019:1008:17
at http://momentjs.com/js/tests.js?_=120203_183019:1589:17
---> Something like "PST"
AssertionError: ---> Something like "PST"
at Object.ok (http://momentjs.com/js/tests.js?_=120203_183019:1526:39)
at http://momentjs.com/js/tests.js?_=120203_183019:2414:14
at Object.runTest (http://momentjs.com/js/tests.js?_=120203_183019:1702:9)
at http://momentjs.com/js/tests.js?_=120203_183019:1748:25
at http://momentjs.com/js/tests.js?_=120203_183019:1006:13
at http://momentjs.com/js/tests.js?_=120203_183019:616:13
at http://momentjs.com/js/tests.js?_=120203_183019:627:25
at http://momentjs.com/js/tests.js?_=120203_183019:1008:17
at http://momentjs.com/js/tests.js?_=120203_183019:1589:17
+02:00 ---> Something like "+07:30"
+0200 ---> Something like "+0700"

@korg250

I also get the same failing test # 28. My timezone is GMT -3.

Agent:
Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.66 Safari/535.11

Failed test: http://pastebin.com/dsWHMF3h

.:.

Agent:
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:10.0.2) Gecko/20100101 Firefox/10.0.2
or
Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; Zune 4.7; .NET4.0E)

Failed test: http://pastebin.com/6t6JP9fu

@timrwood
Moment.js member

So looks like this is happening in UTC+1, UTC+2, and UTC-3.

Unfortunately, there is now way to fix this. It depends on hacking apart the Date().toString() output, and if there is no timezone information available in that string, there is no way to get that information.

I'm going to depreciate this feature and maybe make a plugin that has more reliable (although perhaps less accurate) results. It probably should be something like https://github.com/mde/timezone-js.

@timrwood
Moment.js member

The z zz tokens are being deprecated as of 1.6.0. I'm closing this issue as a result.

@timrwood timrwood closed this Apr 23, 2012
@DjebbZ

What about node.js ? Are z zz reliable or not in this environment ?

@timrwood
Moment.js member

They have been officially deprecated, so they will not work as of version 1.6.0.

For versions of code before that, I imagine the results would also be inconsistant, as Node uses V8 and some of the inconsistant results above are in Chrome, which also uses V8.

@DjebbZ

Thanks. So for a string like Thu Jan 10 2013 22:54:11 GMT+0100 (CET), what I ended up doing is removing with a regexp the timezone string (here (CET) with the leading space) and leaving only the timeshift info (here +0100). Do you think it's enough for moment.js or do I risk inconsistencies ?

@timrwood
Moment.js member

Hmm, I'm not sure what you are trying to do, are you trying to get CET or +0100?

+0100 is supported via the ZZ token (note the capitalization) and works fine when parsing and formatting.

CET was deprecated as we couldn't reliably get it from Date.toString. However, as we use Date.getTimezoneOffset for +0100, the support is much more consistant.

@DjebbZ

I'm doing as you say, using ZZ for +0100 and removing CET from the string to parse. Does it make sense ?

@timrwood
Moment.js member

My apologies, I'm still not understanding what the problem is here. Are you trying to parse Thu Jan 10 2013 22:54:11 GMT+0100 (CET)? You should be able to just do the following.

moment('Thu Jan 10 2013 22:54:11 GMT+0100 (CET)', 'ddd MMM DD YYYY HH:mm:ss [GMT]ZZ');
@DjebbZ

This is exactly what I'm doing at the end. It looks like you're confirming that I'm doing the right thing. My apologies If I wasn't clear, thanks for the answers !

@timrwood
Moment.js member

No problem!

@cozmo cozmo referenced this issue in Clever/gearman-admin Mar 3, 2014
jonahkagan Use 12 hour time and add timezone string cd49a7e
@timrwood
Moment.js member

@hughanderson4, the issue was that browsers don't always return a timezone abbreviation from Date.prototype.toString. Because we couldn't reliably get the timezone abbreviation, it was deprecated.

Since then, moment-timezone has been created to add timezone support for moment.js. You may want to look into that to see if it fits your needs.

@thinkjson

How would one convert a moment.utc() to local time and display the time zone abbreviation?

@machineghost

Stupid question: why an entirely new library? Isn't the point of Moment to solve all of one's date and time-handling needs? While the data files add a non-trivial amount of space (and I can understand separating them), the new library itself is <2k, so space doesn't seem to be a reason for separating it.

It just seems kind of sad that someone who simply wants to generate a date string with a timezone in it has to download two separate libraries and a data file to do what Javascript should have built-in.

Also, how do I use this new amalgamation of libraries to generate a simple date string? Before I could have generated:

Sun, 06 Nov 1994 08:49:37 GMT

with:

moment().format('ddd, DD MMM YYYY HH:mm:ss z');

But now I'm confused as to how I'm supposed to to do that without the "z" formatting option. Any help would be appreciated.

@chris-martin

So, asking just to make sure I understand: There is no replacement for the deprecated 'z' format?

@mrhwick

If I have a timestamp in the ISO-8601 format, such as:

2014-07-25T18:00:00-04:00

And I want to display this timestamp as the following:

6:00 PM EST

Does moment no longer support this formatting? All of the timezone data is included in my timestamp, and I only want to display it directly without transforming the timezone in any way.

@DeadMG

That does not actually include the timezone. There can be several timezone names that correspond to the same UTC offset, especially when considering the possibilities of varying DST. You cannot infer from "UTC-4:00" that the timezone is EST.

@mj1856
Moment.js member

For clarification, the z formatter still works when using moment-timezone with a specific zone - since the abbreviation can be pulled from the time zone data.

@themakshter

Just mentioning this now - if you use
new Date().toTimeString()
you get the same result across all browsers as far as I have tried.

This means that you could possibly use this string to extract the timezone, no?

@Shobana16

Hi I see above that format('z') is deprecated. also in moment docs, i see it is been deprecated from 1.6.0. I am using 2.11.0 now, i can use the 'z' to display timezone (PST/PDT) based on offset.
Should i not to use this 'z' in my code now? can you please tell exact alternative to display PST instead of -/+8

@mj1856
Moment.js member

@themakshter - no, you do not get the same result across all browsers. OS, browser version, and language play into it heavily - and there is no consistency requirement in the spec.

@mj1856
Moment.js member

@Shobana16 - If you just do moment().format('z'), it will always return "".

If you're using moment-timezone, and do something like moment.tz('America/Los_Angeles').format('z'), then you will get a valid response.

z is fine with moment-timezone. It does nothing on a plain moment.

@Shobana16

Thank you for the comments MJ. Yeah i am using 'z' with moment-timezone only. Ok cool will remain my code with 'z'. !

@mj1856
Moment.js member

Just a note to add, as of moment-timezone 0.5.0, you can guess at the local time zone, which opens the door for:

var abbreviation = moment.tz(moment.tz.guess()).format('z');

This is ok, but be aware that:
1. It's just a guess. It might guess wrong.
2. If it does guess wrong, there's still a possibility that the abbreviation could be correct, as many similar time zones will use the same abbreviations, such as how Europe/Paris and Europe/Berlin both use CET and CEST.
3. However, there's no guarantees. If it guesses wrong, you might present the wrong abbreviation.

We might also consider adapting moment.js such that if moment-timezone is available that it could try to do this automatically to re-enable the z formatter. Though this is not happening currently.

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