Multi-language computing has many challenges. During my day to day activities I constantly switch between English and Spanish, and though my whole OS and window manager is set up in English for consistency, I frequently need to type accénted wórds and other characters ñ.

I'm also a big (though novice) user of the agenda present in Emacs orgmode. My problem is that for some unknown reason org timestamps would use days in Spanish instead of English. For example instead of [2022-01-11 Tue] (for Tuesday) it would say [2022-01-11 mar] (for Martes). This being Emacs I knew there had to be a way, just wasn't sure where to look. The usual advice is to set system-time-locale to "en" like this:

(setq system-time-locale "en")
(setenv "LANG" "en")

But it doesn't work for Emacs client instances (when you are using Emacs as a daemon).

The solution in my case is to set the LC_TIME environment variable before Emacs is launched. I use systemd and the unit file is in /usr/local/lib/systemd/user/emacs.service. This is the whole file:

[Unit]
Description=Emacs text editor
Documentation=info:emacs man:emacs(1) https://gnu.org/software/emacs/

[Service]
Type=notify
ExecStart=/usr/local/bin/emacs --fg-daemon

# Emacs will exit with status 15 after having received SIGTERM, which
# is the default "KillSignal" value systemd uses to stop services.
SuccessExitStatus=15

# This is what I added to make Emacs daemon use the proper locale for org timestamps
Environment=LC_TIME=en
Restart=on-failure

[Install]
WantedBy=default.target

Reload, restart and that's it! Happy Hacking!