kimi@sstx:~$ timedatectl 
               Local time: Wed 2022-08-24 07:12:56 UTC
           Universal time: Wed 2022-08-24 07:12:56 UTC
                 RTC time: Wed 2022-08-24 07:12:56
                Time zone: Etc/UTC (UTC, +0000)
System clock synchronized: yes
              NTP service: active
          RTC in local TZ: no
kimi@sstx:~$ sudo timedatectl set-timezone Asia/Tokyo
kimi@sstx:~$ timedatectl 
               Local time: Wed 2022-08-24 16:13:26 JST
           Universal time: Wed 2022-08-24 07:13:26 UTC
                 RTC time: Wed 2022-08-24 07:13:26
                Time zone: Asia/Tokyo (JST, +0900)
System clock synchronized: yes
              NTP service: active

kimi@sstx:~$ localectl
   System Locale: LANG=en_US.UTF-8
       VC Keymap: n/a
      X11 Layout: jp
       X11 Model: pc105
kimi@sstx:~$ localectl list-locales 
C.UTF-8
en_US.UTF-8
ja_JP.UTF-8
kimi@sstx:~$ sudo apt -y install language-pack-ja-base language-pack-ja^C
kimi@sstx:~$ sudo localectl set-locale ja_JP.UTF-8
kimi@sstx:~$ localectl
   System Locale: LANG=ja_JP.UTF-8
       VC Keymap: n/a
      X11 Layout: jp
       X11 Model: pc105