Looks somewhat similar to https://support.mozilla.org/en-US/questions/1235351 However <input type="date"> is correctly localised for me. date is fine. time is not.

I'm happy to take this to Buganizer if you think it is a bug. Thought I should ask here first.

Most locales support 12 hour time which will be preferred, only a few are exclusively 24 hour time like en_IE and en_DK.

On Linux you can change the time locale with the environment variable:

LC_TIME=en_IE.UTF-8

Thank you for your reply.

Most locales support 12 hour time which will be preferred, only a few are exclusively 24 hour time like en_IE and en_DK.

Yes, I think you are right.

As noted in the OP, on Mac platforms, the system provides a specific 24-Hour Time override, which the user may enable independent from other settings. We can see how this interacts with Apple's localisation libraries. Here is a little Swift program...

import Foundation print(DateFormatter.localizedString(

 from: Date(),
 dateStyle: DateFormatter.Style.none,
 timeStyle: DateFormatter.Style.short))

With the 24-Hour Time override enabled in System Preferences, output is as follows.

19:09

With the 24-Hour Time override disabled in System Preferences, output is as follows.

7:09 pm

So perhaps 12-hour clocks are preferred on en-AU as you say.

I suppose the problem is that, on a Mac, Firefox does not use Apple's localisation libraries, and does not honour the 24-Hour Time override in its own implementation for this platform. (Then again, I noticed Safari suffers from the same problem on <input type="time"> elements!)

On Linux you can change the time locale with the environment variable: LC_TIME=en_IE.UTF-8

The equivalent on this platform would be

open -na 'Firefox Nightly' --env LC_TIME=en_IE.UTF-8

or more simply

LC_TIME=en_IE.UTF-8 open -na 'Firefox Nightly'

I gave this a try but it did not seem to impart any effect on <input type="time"> elements.

I reconfigured the Mac for English (Ireland) and restarted Firefox. I see 24-hour input widgets now.

Application Settings Requested Locales ["en-GB"] Available Locales ["en-GB","en-US"] App Locales ["en-GB","en-US"] Regional Preferences ["en-IE","en-AU"] Default Locale "en-GB" Operating System System Locales ["en-IE","en-AU"] Regional Preferences ["en-IE","en-AU"]

This feels like a quirky workaround, but I suppose it will do for now.

LC_TIME is only supported on Linux (GTK).

• https://searchfox.org/mozilla-release/search?q=LC_TIME&path=&case=false&regexp=false
• https://searchfox.org/mozilla-release/source/intl/locale/gtk/OSPreferences_gtk.cpp#31

See also hourCycle:

• https://searchfox.org/mozilla-release/search?q=hourCycle&path=&case=false&regexp=false

I have the same, or at least a related, problem.

Running Firefox under Windows, I have, on Windows, set Regional Format to English(United Kingdom), with Regional Format Data set to give date in yyyy-mm-dd (ISO 8601) format (not the default), and time as HH:mm (which I think is the default).

Looking at - on Firefox - a web page with an <input type="datetime-local"> field, as on https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/datetime-local , I see the date format as dd/mm/yyyy , not yyyy-mm-dd as I would expect (as set in Windows, and appearing on other browsers) - it is using the default option for UK dates, not the ISO option I have changed it to.

Fundamental issue is that Firefox is using the default regional data setting, not the alternate option selected (in the Windows OS locale)

I think this is essentially the same as the OP has, in overiding his normal locale with a non-default option: if not then I have a different problem (beyond Windows/Mac difference)