Locale setting not respected in Firefox

I am using Firefox in Linux Mint for the GUI.
Server is 2.4.13, running on Debian 11

My locale is set to “fr_CH”, but the language is set to “en_US”:
~$ locale
LANG=en_US.UTF-8
LANGUAGE=en_US
LC_CTYPE=“en_US.UTF-8”
LC_NUMERIC=fr_CH.UTF-8
LC_TIME=fr_CH.UTF-8
LC_COLLATE=“en_US.UTF-8”
LC_MONETARY=fr_CH.UTF-8
LC_MESSAGES=“en_US.UTF-8”
LC_PAPER=fr_CH.UTF-8
LC_NAME=fr_CH.UTF-8
LC_ADDRESS=fr_CH.UTF-8
LC_TELEPHONE=fr_CH.UTF-8
LC_MEASUREMENT=fr_CH.UTF-8
LC_IDENTIFICATION=fr_CH.UTF-8
LC_ALL=

The date format in the GUI is “M/d/y”, which I don’t like at all…
A small change in the file “urbackup_functions.xxxxx.js” fixes the problem:
Add “navigator.language” in the line “var lds = y.toLocaleDateString(navigator.language);”

The problem still remains in Chrome…

+1

Thanks for the hint!
I face nearly the same situation and I appreciate the solution. Perhaps it could be incorporated in the next release of urbackup server.