Ubuntu 22.04 automatically update color scheme preference at night

README.md

Place the .timer and .service file in ~/.config/systemd/user

Place the update-color-scheme file somewhere in $PATH

Enable and start the timer

systemctl --user enable update-color-scheme-preference.timer
systemctl --user start update-color-scheme-preference.timer

update-color-scheme

#!/bin/bash

if ! [ -x "$(command -v date)" ]; then
  echo "date is not installed" &>2
fi

if ! [ -x "$(command -v gsettings)" ]; then
  echo "gsettings is not installed" &>2
fi


TIME=$(date +"%H:%M:%S")
# Light mode turns on at 09:00 ends at 20:00
SCHEDULE=("09:00:00" "20:00:00")

PREFERENCE="dark"

if [[ "$TIME" > "${SCHEDULE[0]}" && "$TIME" < "${SCHEDULE[1]}" ]]; then
  PREFERENCE="light"
fi

gsettings set org.gnome.desktop.interface color-scheme "prefer-${PREFERENCE}"

update-color-scheme-preference.service

[Unit]
Description=Updates Prefered Color Scheme

[Service]
Type=oneshot
Environment=DISPLAY=:0
ExecStart=update-color-scheme

[Install]
WantedBy=basic.target

update-color-scheme-preference.timer

[Unit]
Description=Update Prefered Color Scheme Timer

[Timer]
OnCalendar=*-*-* *:*:00
Persistent=true
Unit=update-color-scheme-preference.service

[Install]
WantedBy=update-color-scheme-preference.service