On Tue, 6 Jan 2026, Max Nikulin wrote:
> Hi,
Good time of the day to you.
>
> Some aspects of locales and timestamp formatting have been discussed
> recently.
I have not been around here lately, and did not see that discussion.
> After upgrade to Debian 13 trixie I faced Firefox behavior rather
> surprising for me.
>
> In UI elements I have UK dd/mm/YYYY (not mm/dd/YYYY, expected however) date
> and 12 hours am/pm US time format (that I prefer to avoid). My impression is
> that LANGUAGE environment vairable has higher priority than LANG and LC_TIME
> namely for time (that is unexpected), but not for date. Usually I report
> Firefox bugs to the upstream bug tracker, but due to bookworm vs. trixie
> difference this time I suspect a Debian-specific issue. Can anybody confirm
> discrepancy?
I try to do this below.
> When firefox is not running (or use another profile)
>
> LANG=en_GB.UTF-8 LANGUAGE=en_US:en firefox-esr
>
> Open history [Ctrl+Shift+H] and enable the most recent visit column. What are
> date format and time format?
[rest snipped]
I'm running bullseye (which is currently oldoldstable). I have not yet
upgraded to bookworm.
Yesterday I installed firefox-esr, and used it to visit a couple
websites.
Today I ran the test described in your OP.
Preliminaries: I have no DE. I run startx in a virtual terminal, and
my ~/.xsession launches ratpoison, which is a window manager.
carroll@funafuti:0 ~$ cat .xsession
#!/bin/sh
xsetroot -fg black -bg gray20 -mod 16 16
exec ratpoison -f ${HOME}/.ratpoisonrc
Then, from an xterm:
carroll@funafuti:0 ~$ cat /etc/default/locale
# File generated by update-locale
LANG=en_US.UTF-8
carroll@funafuti:0 ~$ locale
LANG=en_US.UTF-8
LANGUAGE=
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=
carroll@funafuti:0 ~$ locale -a | grep en_
en_GB.utf8
en_US.utf8
carroll@funafuti:0 ~$ LANG=en_GB.utf8 LANGUAGE=en_US:en firefox-esr
./html/home.html
[GFX1-]: RenderCompositorSWGL failed mapping default framebuffer, no dt
[Parent 1067, IPC I/O Parent] WARNING: process 1112 exited on signal 9: file
./ipc/chromium/src/chrome/common/process_watcher_posix_sigchld.cc:134
[GFX1-]: RenderCompositorSWGL failed mapping default framebuffer, no dt
carroll@funafuti:0 ~$ LANG=en_US.utf8 LANGUAGE=en_US:en firefox-esr
./html/home.html
[GFX1-]: RenderCompositorSWGL failed mapping default framebuffer, no dt
[GFX1-]: RenderCompositorSWGL failed mapping default framebuffer, no dt
carroll@funafuti:0 ~$
During both of the above firefox sessions I opened a history window
(using the keystroke shortcut you kindly provided).
LANGUAGE was set to en_US:en on the command line in both sessions.
This is what I see when LANG=en_GB.utf8
Location Most Recent Visit
======== =================
... ...
https://en.wikipedia.org/wiki/Poop 06/01/2026, 13:14
And this is what I see when LANG=en_US.utf8
Location Most Recent Visit
======== =================
... ...
https://en.wikipedia.org/wiki/Poop 1/06/2026, 13:14
As you can see, apparently I have a 24-hour clock in either case.
Miscellaneous considerations (ie, I throw noodles at the wall):
Noodle 1: Ratpoison, my window manager, has a time command, which
AFAICT invariably displays date/time in 24-hour format (and in
English)
Noodle 2: It is unclear to me what the semantics are, of the
preferences in the file below, but here is part of the content of my
own. Conceivably relevant for you.
carroll@funafuti:0 ~$ ls -lAp /etc/firefox-esr/
total 4
-rw-r--r-- 1 root root 1079 Dec 10 03:11 firefox-esr.js
carroll@funafuti:0 ~$ sed '/locale\./ q' /etc/firefox-esr/firefox-esr.js
// This is the Debian specific preferences file for Firefox ESR
// You can make any change in here, it is the purpose of this file.
// You can, with this file and all files present in the
// /etc/firefox-esr directory, override any preference you can see in
// about:config.
//
// Note that pref("name", value, locked) is allowed in these
// preferences files if you don't want users to be able to override
// some preferences.
pref("extensions.update.enabled", true);
// Use LANG environment variable to choose locale
pref("intl.locale.requested", "");
carroll@funafuti:0 ~$
(I tried to attach my full /etc/firefox-esr/firefox-esr.js to this
message, in case you would like to see it, but doing so seems to
prevent me from sending the mail successfully. I doubt it is anything
special.)
Noodle 3: Searching for 'locale' in the preference file for the user
profile I selected (default):
carroll@funafuti:0 ~$ grep locale ~/.mozilla/firefox/********.default/prefs.js
user_pref("extensions.ui.locale.hidden", false);
Noodle 4: Yesterday, when I installed firefox-esr and performed some
preliminary testing, I had
LANG=fr_FR.UTF-8
in /etc/default/locale
instead of
LANG=en_US.UTF-8
I used update-locale last night to change LANG to its present value
(en_US.UTF-8), and rebooted, to see if that would affect the test
results with respect to 12-hour vs 24 hour clock format.
I was unable to see any effect, regarding the results of your test.
That is all I can think of to share.
