Datepicker bug in firefox browser

[Tolitech]

Hello.
I found a bug when using the datepicker component.

Using the firefox version, the month of October is displayed with the incorrect days.

I've tested on Edge and Chrome and both are working properly.
My version of Firefox is Developer Edition.

I created a Plunker with the reproduction that occurs in Firefox and also has the image of the problem.
https://embed.plnkr.co/4WvupnKyZQ8t5oFn1G4l/

Image:
http://www.codegenerator.com.br/images/error.png

[maxokorokov]

Hey, @Tolitech.

Unfortunately you're plunkr is not working (anymore?) for me

However the demos from the site https://ng-bootstrap.github.io/#/components/datepicker are opening fine in plunker with Firefox Developer 55.0b1 on MacOS

Could you please check your plunker?

[Tolitech]

Hi, @maxokorokov.
Thanks for the answer.

Unfortunately the bug also occurs on the demo site.
I am using windows 10.

I downloaded now the latest version of firefox (54.0) and the problem is the same.
In October the days are incorrect.

Image of the demo site:
http://www.codegenerator.com.br/images/ff-error.png

Thank you.

[pkozlowski-opensource]

I can't reproduce despite trying several OSX machines:

@Tolitech are you sure that you are not having any FFox extensions installed? Did you try to reproduce in the incognito mode?

Also, what is your timezone setting?

[Tolitech]

@pkozlowski-opensource

I believe it's only in Firefox versions of Windows.
I have a virtual machine on Azure and I just installed Firefox again.
There was only Chrome.

I installed 64-bit version.
Same problem as 32 bit version on my machine.

I'm in São Paulo, Brazil, UTC -3:00
The virtual machine I tested is in the United States, but I can not remember exactly which region.

I'm trying to figure out some website that will emulate firefox in MacOS and Windows to know if the problem only occurs in Windows.

I do not have any extensions installed.

I'm going to try to find out something else to help, but for all indications, for now it would be the windows version.

[maxokorokov]

Took a look in different VMs with FF Dev 54.0a2 32-bit on SauceLabs.
All Windows 7, 8.1 and 10 look OK.
Machines are in GMT.

So still can't reproduce for now...

[ymeine]

Edits:

• 2017-07-04T14:56:05+02:00: updated the results with Firefox stable (54) in Windows 10

---

So, I tested with several configurations, and here's where I reproduced the bug:

Firefox dev:

	Windows 10 (VM)	Window 7 (real)
UTC-3:00	✔️	❌
UTC	❌	❌

Firefox stable (54):

	Windows 10 (VM)	Window 7 (real)
UTC-3:00	❌	N/A
UTC	N/A	N/A

I didn't investigate further yet, but the result lets think it seems to be a bug linked to the implementation of time on Windows 10 (maybe 8 too). But that's weird that Firefox stable doesn't have the issue in this case.

Procedure to reproduce the test

• launch a Windows machine with the proper Firefox installed
• configure the timezone
  • either using the OS settings
  • or by setting the environment variable TZ to the value GMT+3:00 (syntax and inverted sign are important)
• launch Firefox
• check in the Dev Tools that the timezone offset is 180 by running the code (new Date()).getTimezoneOffset()
• then check the DatePicker normally

Sources:

• Time and time zone settings - MozillaZine Knowledge Base
• Article: How to set TZ variable in UNIX?

Some tips to test on SauceLabs

Since the VM launches with Firefox already started, and that there is no shortcut to launch it again nor access to the disks in the file explorer, do the following:

• open the Task Manager
• check the path of the running Firefox executable
• open a terminal and go to that folder

You'll be able to launch Firefox again from there after closing the previous instance. Even better, with this technique it's straightforward to apply the timezone without having to change OS settings using the procedure above.

[maxokorokov]

Reproduced it locally. Using getUTCDate() instead of getDate() in the datepicker service seems to fix it. Will fix right after #1551 lands